Abstract: Supposing the existance of first reflected waves from the channel surface in underwater acoustic channel,we studied the statistical characteristics of convolutional codes.The results are that,since the decoding of convolutional codes is a deconvolutional operation,the multi-path signals can be resolved by decoding,and can be aligned and superposed in some conditions,then the error probability is reduced;in other conditions,similar results can not be obtained.The capability of antimultipath interference of convolutional codes is similar to the resolution of vertical sonar array in channel,and the multipath signals can be filtered by the sonar array.But the convolutional code is the one easier to be used against the sonar array.Convolutional coeds are good to resist the multipath interference.