Addressed in this paper are the issues of low measuring accuracy, single point measurement and complicated connection of strain gauge about data acquisition used in engineering. By utilization of FPGA technology, an acquisition system of bridge strain based on vibrating wire extensometer was designed, which can simultaneously collect 8-channel strain data, and the frequency measurement method was optimized. Meanwhile, on the basis of the field monitoring of Jinmeng Yellow River Bridge in Shanxi Province, the time-varying mean value method was adopted to study the variation law of strain and temperature data. Finally, the strain was temperature-compensated to obtain accurate data. The experimental results show that: the system has small measurement error, high acquisition efficiency, simple wiring and stable operation. The system has a high application value.