Objective When the nerve fiber is stimulated by the electrical pulse, there is an evoked compound action potential which indicates the synchronism property of the nerve fiber. In order to obtain the precise action potential, a measuring system of evoked compound action potential is presented in this paper. The system can collect the compound action potential precisely and eliminate the effect of ground noise. Methods Firstly, we analyzed the difficulty in the measurement of the compound action potential which ranged from μV level to the mV level. Secondly, we discussed the common-mode tolerance, differential mode tolerance and the voltage margin of the electric current which guaranteed the proper functioning of the measuring system. Based on the issues, we proposed a measuring system of compound action potential which was realized by the operational amplifier using 3-cascade methods. The system consisted of 3-cascade, automatic zero tracking and reference voltage. In this system, the amplification of the weak signal was realized and the background noise was eliminated effectively. Contemporarily, the system provided the efficient overvoltage protection. Results The compound action potential of the frog sciatic nerve which was only 11mV and the electrically evoked compound action potential of guinea pig which was 17μV were measured by this system. The experimental results showed that the accurate compound action potential could be obtained by this measuring system. Conclusions The 3-cascade structure and automatic zero tracking might be an effective way for the effective amplification and precise measurement of small signals. This system supplies a stably measuring method for the further research on the special property when the electrical signal stimulates the nerve fiber directly.