Abstract: The Tibetan Plateau (TP), known as the "Asian water tower," suffered severe desertification internally, with dust aerosol being an important factor affecting precipitation. Clarifying the role of dust in precipitation is essential. In this study, the WRF-Chem model was employed, to simulate a heavy precipitation event occurring on the plateau from June 27 to June 30, 2008. The results indicate that TP dust has different effects on different grades of precipitation by altering the macroscopic conditions and microphysical properties of the cloud. The dust facilitated heavy rainfall, increasing the 24-hour accumulated precipitation by 20.5%, while it exhibited an inhibitory effect on light rainfall, decreasing precipitation by an average of 13.0%. Overall, dust led to a 4.96% increase in total precipitation. The mechanism for this effect is that the dust increased the vertical velocity of heavy rainfall, with the maximum increment exceeding 0.06 m·s-1. Additionally, dust reduced the vertical velocity of light rainfall, inhibiting its upward motion. Dust increased both cloud water mixing ratio and rainwater mixing ratio, with the growth in mixing ratio under heavy rainfall approximately eight times greater than that under light rainfall. Furthermore, dust led to an increase in ice particles under different grades of precipitation and prolonged cloud lifespan.