Abstract: In this study, we systematically examined the impact of artificial ice crystal seeding on cloud microphysical processes and precipitation during a stratiform–convective mixed cloud precipitation event in the Danjiangkou basin on 24 March 2024, based on the Weather Research and Forecasting Model–based mesoscale model coupled with the cloud microphysics program of the Chinese Academy of Meteorological Sciences. This event was controlled by the eastward movement of a mid-latitude westerly trough and the low-level transport of warm, moist air. The results showed that this precipitation process is characterized by the coexistence of warm-cloud and cold-cloud precipitation mechanisms: Warm cloud coalescence dominated the initial-to-peak precipitation stages, while the melting of graupel particles became predominant afterward. Moreover, the target cloud system exhibited a maximum cloud-top height exceeding 12 km, with supercooled water content of 0.01–0.3 g/kg concentrated in a 4–6 km layer, where low natural ice crystal concentrations and updrafts created optimal conditions for cloud seeding. In addition, seeding with artificial ice crystals, under the synergistic effect of warm- and cold-cloud precipitation processes, initially reduced the ground precipitation in the affected area, which later increased. Within 30 min postseeding, ice crystals grew through deposition and aggregated with snow particles, resulting in an increase in the snow mass mixing ratio. However, the increased snow particles failed to descend into the warm layer for melting, while reductions in cloud droplets and graupel weakened the process of collision–coalescence and graupel melting, leading to decreased surface precipitation. From 50 min to 3 h postseeding, enhanced graupel collection of snow crystals and graupel melting in the downstream region provided large initial raindrops to the upper warm sector, thereby intensifying raindrop collision–coalescence with cloud droplets. This ultimately enhanced warm- and cold-cloud precipitation processes, resulting in greater surface rainfall. The total 3-h accumulated rainfall increase across the evaluation area reached 2.438 × 10⁵ t. Sensitivity experiments showed that excessive ice crystal seeding reduced rainfall enhancement by depleting water vapor and weakening graupel production. Among single-layer seeding experiments, the 5.2 km (−7℃) layer yielded the optimal rain enhancement results. Therefore, synergistically optimizing the seeding dose and height in stratiform–convective mixed clouds can considerably improve the precipitation efficiency, providing a scientific basis for cloud-water resource management in the Danjiangkou basin.