A parameter estimation algorithm based on data assistance is proposed to estimate the parameter estimation problem of single channel cofrequency mixed signal with fixed frame length and frame synchronization sequence in noncooperative satellite communication. First, the algorithm estimates the frame length and the beginning position of the frame head and extracts the frame synchronization data to construct the auxiliary function. After correlating with mixed signals, the interference term is removed, and the precise estimation of frequency offset is obtained by peak search. The auxiliary function is used to simplify the mixed signal, and then the initial information of the signal is extracted based on the maximum likelihood estimation theory. Finally, the estimation of the signal frequency offset and the initial phase of the signal is realized. Based on algorithm research, the modified Cramer-Rao bound for parameter estimation of single-channel cofrequency mixed signals is derived, which provides a theoretical basis for the performance analysis of the algorithm. The simulation results show that when the frame synchronization signal reaches a certain number, the variance of frequency offset is 10-7, and the initial phase variance is 10-3.The performance of the algorithm is close to the MCRB theory.