In order to improve the performance of cumulant-based identification algorithm existing timing error, a modified algorithm which has better stability and higher recognition probability is presented. Firstly, model of mixed signals is used in cumulant expression. Then, effects of unknown parameters, such as over sampling ratio, timing error and based-band pulse-shaping function are all analyzed quantitatively. Further, an improving method which can reduce the effects of factors that affect performance of recognition obviously is given. The experiment results show the validity of the modified algorithm.