The invention discloses a low-complexity underwater acoustic channel estimation algorithm based on orthogonal matching pursuit, and relates to a low-complexity underwater acoustic channel estimation algorithm based on orthogonal matching pursuit. Firstly, ignoring a Doppler spread factor, and establishing a solution space required by a PSO algorithm on a time delay dimension; secondly, optimizingan inertia weight coefficient in a PSO algorithm, and searching a most matched atom set in a solution space, namely, an initially estimated path delay set; thirdly, expanding the initially estimated path delay set, and establishing a solution space required by the PSO algorithm again in combination with a Doppler spread factor; and finally, searching the most matched atom set by adopting a PSO algorithm to obtain an underwater acoustic channel impulse response estimation value. An inner product storage index table is established in the process of searching the most matched atoms twice, so thatrepeated calculation of the inner product is avoided, and the searching speed is increased. On the basis of an existing OMP algorithm, a two-step estimation method is adopted, the number of times ofinner product calculation can be reduced, and the complexity of the existing OMP algorithm is effectively reduced.