A direct signals cancellation algorithm for passive radar based on Total Least Square(TLS) is proposed. First, the number and delay of direct signals are obtained by TLS, then the subspace of direct signals is constructed based on the available information of direct signals. Finally, the echo is projected into the sub-space to realize direct signals cancellation. Compared with the traditional extended cancellation algorithm, the direct signal sub-space constructed by this algorithm has low order and high precision, and it still has good clutter suppression performance in the case of short processing time or time-varying amplitude of direct signals. The simulation results verify the effectiveness of the proposed algorithm.