Matrix gradient coils were proposed for spatial encoding showing their potential to offer high flexibility in generating customized spatial encoding magnetic fields [1, 2]. The generation of specific spatial encoding magnetic fields may be very flexible if each coil element is driven by its own amplifier. However, if the number of amplifiers is equal to the number of coil elements, the costs might become unacceptable. To address the increased cost of an increased number of independent gradient amplifiers, Kroboth et al., have introduced an optimization method to use a limited number of gradient amplifiers to drive higher number of coil elements simultaneously for given target fields [3]. In this work, we present the design and implementation of a multi-channel gradient driver system for a matrix gradient coil.The block diagram of gradient driver system is shown in Fig.1. A 12 channel 150A/350V amplifier system (4*XPA-150-350, IECO, Helsinki, Finland) is available to drive the matrix gradient coil in our lab. A commercial 32 channels high-speed digital IO board (PCIe-6536, National Instruments) generates digital gradient waveforms and switching codes in real-time with 100MB/s high speed data rate. The high-level pulse sequence is defined using the open-source pulse sequence programming environment, Pulseq [4, 5]. The Pulseq console was extended to simultaneously control the additional amplifier channels and the Siemens system for RF pulses, traditional gradients and signal acquisition. A waveform file for the additional gradient channels is sent to the PCIe-6536 based gradient waveform generator to generate digital waveforms. The generator software was written in the graphical programming language using LabVIEW 2012 (National Instruments). The LabVIEW-based GUI generator loads the gradient waveform file, and then interprets these files to meet the data format requirement of PCIe-6536. The interface board provides the connection between PCIe-6536 and home-build DACs board. A Fiber Optic transmitter (AFBR-1624, Avago technologies) converts the TTL signal to an optical fiber signal with galvanic isolation. The external trigger signal is provided by the Siemens console to start the gradient waveform generation. To synchronize the gradient power amplifier and PCIe-6536 with the Siemens console, an external 10MHz reference clock from the Siemens console is used. Since the 10MHz reference clock is a 3dBm sinusoidal signal, the clock distribution board was implemented to convert the sinusoidal signal to a TTL signal and distribute up to 12 TTL clocks with low jitter. Each XPA-150-350 includes a three channel analog-control gradient power amplifier, and each amplifier can support 31 different coil loads. A 12 channel DAC board was implemented based on a high precision 18 bit DAC (AD5781, Analog Devices) to convert the digital waveform to meet the input requirements of gradient power amplifiers. A load parameter control board is used to change the proportional-integral-derivative (PID) parameters stored inside the gradient power amplifier when the coil combination is changed. These different coil load parameters are stored on the amplifier ahead of the experiment through a serial port RS-232.The 12 channel commercial gradient amplifier and home-built electronics are shown in Fig.2. The front panel of the LabVIEW GUI generator is shown in Fig.3. A newly constructed matrix gradient coil with 84 elements was used for testing [6]. Groups of three to eight coil elements were serially connected in 12 clusters driven by the implemented system. The field maps of 12 clusters were acquired using a single uninterrupted GRE-sequence on a 3T Trio scanner (Siemens Healthcare, Erlangen, Germany), as shown in Fig. 4. A phantom image with linear encoding fields generated by the same clusters was also acquired successfully (the results are not shown here). Switching functionality of the driver system was tested separately, but was not used in this initial work.A 12-channel gradient driver system was constructed and tested successfully with a matrix gradient coil with its channels grouped in 12 clusters.