Abstract: Based on data of conventional observations, hourly observation of automatic station and microwave radiometer, we analyzed the causes of two heavy rain and snow processes in Urumqi on March 17-18 and April 11-12, 2018（referred to as“03·18”process and“04·11”process）. According to the results, the two processes occurred under the circulation background of the two ridges and one trough. The central Asian trough moved eastwards and affected northern Xinjiang. The circulation configurations maintained by heavy precipitation were the southwest airflow, low-level northwest flow,and wind shear in the middle and high-rise troughs near Urumqi. The analysis of microwave radiation data in Urumqi showed that the temperature change trend of both processes was the same at 1.2-1.5 km,and the temperature of the rain turned to sleet was slightly higher than that of sleet turned to snow.However, during the“03·18”process, the temperature of rain to sleet was lower than that of sleet to snow, while the process of “04·11”is opposite. The surface temperature of-0.4-0.5 ℃ and-2.5-3.0 ℃ at 1.5 km were used as a reference indicator for sleet. The values of water vapor density and liquid water content below 3 km are the highest in pure snow, the second in the transition from sleet to snow, and the smallest in the transition from rain to sleet. The humidity below 4 km was greater than 80%, and the value of the“04·11”process is obviously higher than that of the “03·18”process. The water vapor density and liquid water content reached the maximum 10.6-12 g·m^-3 and 0.4-0.8 g·m^-3 during the two heavy snowfall processes,respectively.