Abstract: Stratiform clouds with embedded convections are important precipitation systems in Beijing. Aircraft observation data are combined with the mesoscale numerical simulation model WRF to analyze a stratiform cloud system with embedded convections and related precipitation process in Beijing area that occurred on 23 September 2014. By analyzing the radar echo evolution of the cloud system, it is found that there was no explosive growth in the convective bubble in the cloud, and the echo was not obvious in the vertical direction. Therefore, this process was a horizontal mixed cloud system precipitation process. The analysis of aircraft observations shows that the liquid water content of the cloud system in the morning and afternoon was not high (the maximum was less than 1 g/m³). At different heights of the cloud system, the shape of ice crystals detected by the aircraft mainly consisted of plate, needle column, radial as well as irregular. Due to the relatively small amount of supercooled water in the cloud, the number of aggregated ice crystals was significantly more than that of the attached ice crystals. The polymerization process of ice crystals was the main process of particle growth in the cloud. The analysis of the source and sink terms of the vertical microphysical structure of the cloud system and the precipitation particles indicates that at upper levels, the ice and snow crystals produced by condensation continuously aggregated, grew and fell in an environment with less supercooled water content. The graupel content was very small, and the melting of ice and snow crystals near the 0 ℃ layer was the main mechanism for generating ground precipitation. In addition, near the melting layer, raindrops catching cloud droplets and falling to the ground were another important source of ground precipitation.