Abstract: Emerging services such as substation mobile inspection have higher requirements for wireless coverage quality. In order to improve the signal coverage capability in non-line-of-sight area, the indoor signal coverage performance analysis and modeling simulation with the assistance of reconfigurable intelligent reflector (RIS) are carried out. According to the characteristics of two cascaded sub-channels of RIS assisted communication, ray tracing (RT) technology is used to process the signal and obtain the electromagnetic propagation characteristics. RIS reflects the signal from the sent signal to the weak area after phase regulation, and the receiving end receives the multi-path information assisted by RIS to enhance the coverage performance. In order to reduce the computational cost of tracking, an approximate model based on non-reflective path is proposed. Finally, the received power, power delay spectrum, delay spread and calculation cost are simulated and compared respectively. The experimental results show the influence rules of RIS on signal transmission performance, i.e., neglecting the reflection loss and non-ideal reflection characteristics of RIS in practical applications, its assisted transmission can significantly improve the effective coverage rate of signals, and the approximate model can achieve an effective trade-off between accuracy and computation time.