Abstract: By using probes of FSSP-100, GA2 and GB2 of an airborne PMS (Particle Measuring System), the stratocumulus clouds during August to September in 2004 over Beijing and its surrounding areas were probed. The results showed that the diameter of particles was primarily distributed around 5－9 μm, 200 μm and 400－1000 μm. On 14 September 2004, the warm frontal stratocumulus presents the maximum number concentration of 318.97 cm-3, 0.03 cm-3, and 0.0065 cm-3measured by FSSP-100, GA2, and GB2, respectively. On 12 August and 15 August, 2004, controlled by the cold frontal system, several dry layers were observed. The size distributions of particles derived from probe GA2 in the three flights mainly followed unimodal distribution and the better fitting function was found. Based on the analyses of two-dimensional images of probe GA2, the unimodal distribution was primary for different particles of natural condition. The supercooled cloud and rain water, graupel, columnar and needle crystal have the same order of number concentration above 0 ℃ layer in the cold frontal clouds. The peak content of supercooled water was 0.26 g/m3. In the warm frontal clouds, graupel, riming particles, and large aggregates were the main ice particles, and the supercooled water, columnar and needle crystals were measured. Compared with the GA2 data above the layer of 0 ℃ for 13 flights over northern China, stratocumulus clouds over Beijing and its surrounding areas present the maximum diameter of ice and snow crystal, the middle number concentration, and different content of supercooled water depending on different stratocumulus structures.