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Based on the observation data of Shenyang X-band dual-polarisation phased-array radars (XPAR-D) and S-band radar (CINRAD/SC), combined with minutely precipitation data collected by automatic meteorological stations in Shenyang, this paper analyses the characteristics of a short-time heavy rainfall process that occurred in Shenyang on September 18, 2023. The results are as follows. The comparative observation results of XPAR-D were more detailed. However, its detection capability for weak radar echoes and those that were far away from the radar were weaker than that of the SC radar. The comparative observation results show that the SC radar had a larger coverage area and a more complete structure than XPAR-D. In the area with less influence of electromagnetic attenuation, the detection capabilities of the XPAR-D and SC radar in terms of the structure and intensity of the reflectivity factor and radial velocity were basically comparable. The area of strong echoes of the XPAR-D was wider, while the area of the region with high wind speed of the SC radar was larger. The rapid development and maintenance of the relatively strong echoes of XPAR-D, the relatively large values of CR and Z_DR, as well as the sharp increase and maintenance of the K_DP value jointly contributed to the occurrence of this short-time heavy rainfall. Before the precipitation started, the detection results of XPAR-D often showed large values of Z_DR. The rapid increase of CR and the abnormally high value of Z_DR had good indicative significance for the onset of precipitation. After the onset of the short-time heavy rainfall, there was a good corresponding relationship between CR and Z_DR, which effectively indicated the duration and variation trend of the heavy precipitation. The sharp increase of K_DP served as a warning for high values of minute precipitation, and the value of K_DP more intuitively reflected the intensity of minute precipitation. During this short-time heavy rainfall process, the Z_DR column in the XPAR-D observation results was located on the left side of the updraft of the convective cell, which corresponded well to the location of the weak echo area, and there was a separation phenomenon between the Z_DR column and the K_DP column. The high-value band of K_DP value corresponded to the strong echo centre of the convective cell, and the K_DP column corresponded to the heavy precipitation centre on the ground. Although the radial velocity results detected by XPAR-D during this short-time heavy rainfall event didn’t meet the criteria for a mesocyclone, they indicated that weak eddies also had the potential to enhance precipitation.