Abstract: A greedy pilot assignment based on location with pilot power control algorithm (GPABL with PPC) is proposed for the serious pilot contamination problem in the uplink training phase in cell-free (CF) massive multiple-input multiple-output (MIMO) systems. Based on the principle that neighboring users are not assigned the same pilot sequence, the greedy pilot assignment (GPA) is performed. Then, the pilot power control is superimposed on the base of pilot assignment, and a reasonable pilot power control coefficient is chosen to reduce the mean square error of channel estimation. Simulation results show that the joint use of the two pilot optimization strategies can significantly improve the throughput of the system.