Abstract: We propose a method of underwater target passive ranging based on the sparsity of the target space and the mechanism of focused beamforming. First, we mesh the distribution space of the signal sources according to the method of forward distance and backward distance. Second, we establish the model of received data with uniform linear array based on a spherical wave propagation. For each direction in space, we construct a complete array manifold matrix as a sensing matrix at uniform distance, and construct a convex optimization model for the underwater target signal estimation in the corresponding direction based on the compressed sensing theory. Third, we use a basis pursuit algorithm to solve the convex optimization model, and estimate the energy of the target signal in each direction and distance. Finally, we find the passive direction and the range of underwater target by searching the peak signal energy in the whole space. The simulation results show that the proposed method achieves a high focusing efficiency in range estimation and can effectively solve the problem of low range resolution of the conventional focused beamforming technology; moreover, it can find the passive directions and ranges of multiple independent narrowband underwater targets.