Typhoon “In-fa” was generated on July 18, 2021, and became an extratropical cyclone on July 30, with a life history of 13 days. It affect-ed 14 provinces and cities in eastern China. The main characteristics of typhoon “In-fa” include slow moving speed, long retention time on land, and large cumulative rainfall. Based on multi-channel observations and products from geostationary meteorological satellites, precip-itation measurement satellites and polar-orbiting meteorological satellites, this paper presents a preliminary analysis of the influence pro-cess of “In-fa. The main results are as follows. Firstly, the scale of “In-fa” is large (about 350 km radius at the maximum), the convection is deep and the spiral characteristics of the cloud system are significant before landing. After landing, the cloud system structure was de-stroyed, and the medium convection is densely distributed but unorganized. Secondly, when “In-fa” was on the ocean surface, the liquid water and ice water are rich and show asymmetric distribution. After landing, the liquid and ice water were mainly concentrated on the right side of the typhoon’s forward direction. Thirdly, the retrieved rain rate based on microwave imager show that the precipitation is mainly distributed in the spiral rainband around the typhoon, and the position and area are in good agreement with the actual situation. Although there is a certain deviation between the estimated rainfall and the actual situation, it is still useful for precipitation forecasting, especially in regions where conventional data is scarce.