Different neural signal blocking technologies provide potential therapy for various diseases caused by pathological or involuntary neural activities. In this paper, a novel neural signal blocking concept based on spike-trapping principle is introduced. The blocking system was designed and implemented. In the system, a compound action potential was induced by a proximal stimulus, and a blocking signal was generated after a neural signal was detected, which was applied to the distal end of the nerve to block the nerve conduction. The reliability of the system was verified on bullfrog sciatic nerve gastrocnemius muscle specimens. The optimal blocking signal parameters, the relationship between nerve diameter and blocking threshold voltage, and the nerve safety of blocking signals were explored. The experimental results show that the system is possible to block a pathological or involuntary neural signal automatically. The average voltage of block threshold and the minimum pulse width are -1.66 V and 120 ms, respectively. The blocking threshold decreases as the diameter of the nerve increases. The blocking signals at the threshold level are safe for the stimulated nerve.