Abstract: As urbanization accelerates, hazards including flash floods, debris flows, and urban inundation are becoming more frequent and severe, with escalating social disruption and economic losses. A scientific and effective radar quantitative precipitation estimation (QPE) product is essential for enhancing the monitoring, forecasting, and early warning of extreme precipitation, which is of great value to current disaster prevention and mitigation efforts. This study used data from a single S-band dual-polarization radar and six X-band dual-polarization phased array radars in Jiaxing to develop S-band and X-band radar QPE products for the region. After preprocessing the radar observation data, including removing nonmeteorological echoes and performing quality control of the differential propagation phase, the effective minimum hybrid elevation for each radar was calculated. Then, the rain rate was estimated using single radar observations and raindrop size distribution parameters provided by the Dual-frequency Precipitation Radar onboard the Global Precipitation Measurement satellite (GPM-DPR). Finally, the rain rate was mosaicked for multiple radars, forming a gridded QPE product with a temporal resolution of 1 min and a spatial resolution of 50 m. To verify the accuracy of the proposed method, two heavy precipitation events that occurred on 10 and 16 September 2024, in the Jiaxing area were selected to evaluate the radar QPE products. The evaluated products included the original Jiaxing X-band QPE product and the X-band, S-band, and mosaic products developed in this study. The results show that the proposed QPE products outperform the original X-band product in terms of accuracy and stability, with the mosaic product yielding the best estimation result. For localized heavy rainfall with horizontally inhomogeneous distribution, the mosaicking product accurately reflects the precipitation distribution across various towns (subdistricts), contributing to the early issuance of accurate warnings.