The inter-carrier interference (ICI) in passive optical network (PON) systems based on orthogonal frequency division multiplexing (OFDM) technology is resulted in seriously by kinds of fiber nonlinear factors. An algorithm based on the pseudo-symmetrical training (PST) sequences is proposed to solve the problem; two Toeplitz sub-systems which are transformed from the mentioned problem are to be solved. The input of the second sub-system is achieved by pre-processing the first sub-system. As a result, the output of the second sub-system can be achieved based on least square (LS) criterion. At last, the suppression of ICI can be achieved. The characteristic of PST sequences and fast Fourier transform (FFT) are introduced into the proposed algorithm refraining from traditional high order inversion. As a result, the real-time performance of the calculation is improved. Simulation results show that the proposed algorithm for OFDM-PON systems can not only suppress ICI, but also improve the real-time performance dramatically.