Since the concept of random fiber laser was proposed, it has received extensive attentions in the fields of fiber lasers, fiber sensing, etc. Combining random fiber laser with fiber grating, high performance point-sensing system can be realized based on spectral change information of fiber grating. Therefore, the spectral characteristics of this system determine key parameters such as sensing distance, accuracy and multiplexing capability. Aiming at the key issue of high-order random laser multi-point sensing system, i.e., spectral characteristics simulation, this paper improves the traditional high-order random laser power balance model, and the spectral simulation results of the proposed model are in good agreement with the experiment. Based on the simulation model, a high-order random fiber laser multi-point sensing system with a length of 150 km is designed and realized. At the same time, the fitting linearity of the sensing signal wavelength and strain obtained from the experiment is as high as 0.999, which fully verifies the system’s sensing performance.