The invention belongs to the technical field of communication safety, and specifically discloses a method for reducing a safety gap of a COFDM system. The method is based on a complete communication system environment, an information bit stream is output at a source of an emission end, channel encoding, Yarg-code mapping, constellation puncturing, serial-parallel conversion, inverse fast Fourier transform, parallel-serial conversion and CP adding operation are carried out on the information bit stream, a receiving end employs an algorithm opposite to the emission end, and finally, the information bit stream is recovered. According to the invention, a Yarg-code mapping method and a constellation puncturing technology are combined and are applied to a COFDM system, through performing puncturing zero-setting on constellation points on a Yarg-code constellation mapping graph, puncture positions are enabled to be not easily recovered under a signal-to-noise ratio and can be completely recovered under a high signal-to-noise ratio, the system bit error rate is enabled to be higher under the low noise-to-signal ratio and is more rapidly reduced under the high signal-to-noise ratio, and thus the purpose of greatly reducing the system safety gap is realized.