The data acquisition system designed in the paper adopts a double CPU construction with DSP and MCU. Data acquisition and control function and data processing and communication function are separate and completed by two units. One unit fulfills the real-time acquisition of signals and the control of periphery actuators. The other unit completes the data processing and communication between Ethernet and the upper computer. At the same time, the data acquisition system adopts a modularized method to design corresponding hardware circuits of different modules. The software designing uses a modularized programming method which is from the top to the bottom, and refined gradually. The data acquisition system designed has characteristics of sample construction and good real-time performance, solving the contradiction between applications of Ethernet and backward industrial I/O equipment.