Analog signal is one of the key data types of flight control computer.We designed a kind of A/D conversion unit with high speed, high precision and strong inhibiting ability to the noise and electromagnetic interference.To suppress and eliminate the noise interference and improve the stability of the A/D sampling data, we used the differential signal acquisition circuit, combining with the hardware and software design of the filter.The test results showed that:under the condition of typical interference, the high precision A/D units resolution of data acquisition reaches 15 bit and the accuracy is 14 bit.Compared with the original example of flight control computer, the A/D data acquisition precision is increased by 2~3 bits and flight control computer works stably, which meets the requirements of UAV flight control computer analog data acquisition.