In order to meet the demand of high speed and high precision in the multi-channel pneumatic system, the problems of on-off speed in data acquisition and its characteristics were investigated. First, parameters and structures of the state-of-the-art multiplexer model were introduced evaluated by calculating and analyzing the relationship among on resistance, equivalent capacitance and setup time of the single polarity multiplexer. The analysis results provide the bases for determining the on-off speed. Second, the transmission effect of sample-and-hold circuit and the principle of optimization were examined by analyzing the settling time of a multiplexer. Last, the design standards were proposed based on the aforementioned results. According to the application requirements, ADG508 Multiplexer was chosen to develop a multi-channel, high-speed and high-precision data acquisition circuit of a pneumatic servo controller, including filter circuit, multiplexer and CPLD-based ADC drive. Laboratory and field tests were conducted and results indicate that the maximum sampling speed is up to 20ksps under the condition of 0.05% precision.