Multi-target detection based on the time-reversal imaging with multiple signal classification (TR-MUSIC) and back-projection (BP) algorithms is presented in this paper. In the TR-MUSIC, firstly, the backscatter of a signal transmitted into a scattering environment is recorded. Secondly, the time reversal operator is obtained with the use of transfer matrix. Finally, the targets can be located through back-propagation of the eigenvectors of time reversal operator. In the BP, the imaging map is reconstructed by using the power of the electromagnetic wave corresponding to the travelling time from the transceivers to each pixel in imaging region. The imaging basic theories of TR-MUSIC and BP algorithms are outlined. In order to illustrate the performance of these two algorithms in detail, numerical simulations for three ideal point-like targets are conducted and analyzed. Here, we consider two versions of the simulation: targets detection with enough detection elements or not. Results show that the TR-MUSIC approach has a better performance than BP approach.