The invention discloses a sparsity self-adaptive OFDM (Orthogonal Frequency Division Multiplexing) system channel estimation method and belongs to the technical field of mobile communication. The method comprises the following steps of 1, obtaining channel response at a pilot frequency, 2, establishing a channel model, 3, constructing an observation matrix and an observation value both needed by signal reconstruction, and 4, recovering channel impulse response according to a reconstructing algorithm. The method achieves the goal of high channel estimation performance even though a prior condition that the channel sparsity is known is not satisfied, and therefore, a simple and efficient solution is provided for sparse channel estimation; the method is capable of reducing the number of the pilot frequencies, improving the spectrum efficiency and effectively reducing the error of channel estimation.