Abstract: In order to get the self-synchronizing scrambling information of the unknown lines in digital communication, a method of order estimation of self-synchronizing scrambling polynomial is presented. Through deeply studying the run property of self-synchronizing scrambled sequences, the corresponding relationship between the result of run statistic and the order of the self-synchronizing scrambling polynomial is gained. With this relationship, after calculating the run statistic with different length using the received scrambled sequence, the self-synchronizing scrambling polynomial order of the unknown line will be estimated through the distribution of the run extremums. The results of experiment verify the correctness of the theory analysis and the validity of the whole method.