The coefficient inverse problems occur in many fields of natural science and scientific engineering such as geophysical exploration and medical imaging. In this talk, I will introduce the recent work on the convergence rate of Tikhonov regularization for a coefficient problem of the wave type equation in general dimensional spaces with Robin boundary condition. To solve the problem, a suitable minimum functional is established. Then it is proved that the functional attains a unique global minimum. Finally, the convergence rate of the Tikhonov regularized solution of the coefficient problem can be obtained without the smallness requirement on the source function.