In this paper, the precipitation cloud system of southwest vortex weather on 3 May 2017 was analyzed based on the observation data of Ka-band cloud radar, microwave radiometer and micro rain radar at Huangsi National Observation Station in Xingtai, Hebei Province. The results showed that this precipitation process was a stable stratiform cloud process. And the falling speed of particles in the cloud gradually increased from high level to low level. The precipitation first appeared in the developing stage of cloud, and then in the mature stage of cloud. The curves of relative humidity, water vapor content, liquid water content and temperature in the cloud appeared to jump and peak at the same time before raining every time. All the indicators obviously declined after the end of precipitation, then recovered and rose to the second and third peaks with precipitation. The microwave radiometer data were continuously used to retrieve “cloud vapor pressure and ice-saturated vapor pressure difference (e-Ei)” in time and space. When the supercooled water and the large-value area of supercooled water vapor in the cloud coincides with the positive area of e-Ei, the Bergeron process is relatively strong in cold clouds, which is helpful to quantitatively determine the location of heavy precipitation and the potential area for artificial precipitation. Based on the data of cloud radar, microwave radiometer and micro rain-radar, we think that there were two chances for weather modification operation during the rainfall process of this time. The first chance was from 13:45 BT to the time when the cloud top dropped to 6 km, and the second was longer, and the cloud condition was more favorable for operation. That was the period from 17:40 BT to 21:15 BT when the cloud top height was maintained at the 8-10 km height. What’s more, the suitable working height was from 4 km to 8 km (-20-0℃).