The microphysical characteristics and different snow liquid ratios (SLR) of rain to snow and snowfall processes during the same period of Beijing Winter Olympics were analyzed based on Parsivel data, densely artificial snow-depth measurement and microscopic snowflake shape observation. The average particle spectrum showed a unimodal pattern, with snowflake spectrum having the highest peak number concentration and raindrop spectrum having the lowest. During the same snowfall process, the peak number concentration of plate or column ice crystals was higher than that of dendritic snowflakes. The average falling speed of particles falling below 2 m/s can be used as an indicator of phase transfer. The average falling speed of dry snow particles was less than 1 m/s. The ambient air temperature during the rain to snow process on February 13-14, 2020 was relatively high. The growth of snowflakes in the sleet stage mainly came from the riming process. With the decrease in temperature at lower levels and the significant increase in humidity at -18~-12℃ layer, precipitation phase turned to snow and the riming process still existed. Under the joint action of riming and adhesive aggregation processes, the maximum crystal diameter reached 19mm, but the snow liquid ratio was low to 0.6cm/mm. In the snow process during the Winter Olympics, the temperature was lower with low level cloud region between -18 and -12℃, and the falling velocity was close to the classical curve of the unrimed ice crystals, so the snowflakes were all unrimed. The combined action of sublimation, Bergeron process, and hook aggregation made the particle diameter grow to 11mm. But the snowflakes’ shape changing to plate or column was observed at Shougang Venue, resulting in the increase of the number concentration and reduction of particle spectrum width, while the corresponding SLR sharply reduced.