Full matrix focusing method has been proved with the advantages of good signal-to-noise ratio and high-resolution image. However, it is still suffering from the problems of the time-consuming data acquisition and processing. In order to solve the problem, two kind simplified matrix focusing methods are provided in this paper. One is a triangular matrix focusing algorithm based on the principle of reciprocity for the multi-channel ultrasonic system. The other is a trapezoidal matrix focusing algorithm based on the energy weight of the different channel to the imaging area. In order to prove the validity of the provided algorithms, both side-drilled hole and oblique crack defects are used for the imaging comparation. The results show that the imaging quality of the triangular matrix focusing algorithm is basically consistent to that of the full matrix focusing method, and the imaging quality of the trapezoidal matrix focusing algorithm can be slightly reduced as the amount of multi-channel data decreases. In addition, both data acquisition and computational efficiency using the provided algorithms have been improved significantly.