Abstract: A 512-channel signal readout system for the multi-channel micropattern gas detector was designed and tested. In this system, a Spartan-6 FPGA was used as the controller and processor. A 4-channel ADC was employed to convert analog signals output to digital signals by 4 APV25s synchronously. The data and commands between FPGA and computer were transmitted by gigabit Ethernet. Two threads were used for data sending and receiving separately at the computer end. The test result shows that the noise of the system is lower than 2 000e when the input capacitance is smaller than 200 pF. The effective range of charge input is ±20 fC and the linearity is very good below 12 fC. Long time tests show that the system is stable with the speed of Ethernet reaching 940 Mb/s. The continuous trigger rate can reach the upper limit of APV25 (285 kHz) for 1 APV25 and 134 kHz for 4 APV25s. Good results were obtained in the imaging experiment of GEM detector with α ray and this system.