To deal with the severe influence caused by phase noise in the coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, a novel phase noise suppression algorithm based on the linear-interpolation and the Kalman filtering is proposed. The novel algorithm linearly combines the time domain signal at the receiver, and then preliminarily suppresses the phase noise using the linear interpolation method in the first stage. In the second stage, the residual phase noise is suppressed with the technique of the Kalman filtering. The analysis of the simulation results shows that the proposed two-stage algorithm can effectively suppress the influence of the phase noises on the OFDM symbols and apparently reduce the error floor at the condition of the large phase noise. The BER performance can reach below the level of 10-7 and the performance of the system can effectively be improved by using the proposed two-stage algorithm.