The severe convective rainstorm that occurred on the west side of Liupan Mountains on 15 July 2022, which is missed by both the numerical weather prediction models and the subjective forecast of forecasters, is analyzed based on the data from regional weather stations, X-band dual-polarization weather radar, C-band Doppler weather radar, wind profiler radar, and the ERA5 hourly reanalysis and conventional observation data. The results show that the rainstorm occurred in the northwest side of the western Pacific subtropical high. The main area of severe rainfall was the south side of the low-level shear line and the left-front side of the low-level jet. Affected by the terrain of Liupan Mountains, the mesoscale ground convergence line, mesoscale low-level southwest jet and mesoscale vortex might be important systems of triggering, maintaining and enhancing of the process. The rainstorm was caused by two mesoscale echo bands, on which the convective cells propagated backward, forming obvious train effect. The strengthening low-level jet, the increasing vertical wind shear, the downward disturbance of wind speed in the jet, and the dry intrusion appeared 1-2 h ahead of the increase in 5 min precipitation, which has a certain reference value for rainstorm forecast and early warning. The center of severe rainfall has a better corresponding relationship with the echo area with intensity ≥50 dBz and the large value area of vertical integrated liquid water, the echo tops, the large ranges of differential phase shift (KDP) and differential reflectivity (ZDR). KDP is a good indicator for intensity of severe rainfall. The maximum values of KDP and ZDR appeared 10 min earlier than the maximum rainfall in five minutes. The ZDR arc and ZDR column also appear 10-20 min earlier than the maximum rainfall. During the heaviest rainfall period, the KDP was 3.0-4.0 °·km-1, the ZDR was 3.0-3.3 dB, and the correlation coefficient was 0.90-0.95, which suggests that the spectrum of rain particulates contained a large amount of relatively large-sized raindrops, increasing the extremity of precipitation.