The key problem for OFDM (Orthogonal Frequency Division Multiple) systems is who to Estimate carrier frequency offset (CFO) with reduced complexity and acceptable performance. The CFO must be compensated before DFT (Discrete Fourier Transform) in order to restore data correctly and enhance the system performance. This paper, present a low complexity estimator of CFO with Semi-Blind (SB) criterion based on pilot tones and on virtual subcarriers, and with the aid of subspace based method. However, MUSIC and ESPRIT based semi-blind algorithms require a highly computational complexity. To overcome this drawback, we use Taylor’s series for the first order as developed in [1]. The present methods developed in this paper are very suitable for Multi- Carrier (MC) systems when the CFO are present. Simulation results demonstrated that the semi-blind (SB) approach outperforms the blind-based approach.