In order to study microphysical characteristics and changes of snowfall in Nanjing, observations of the second-generation laser raindrop spectrometer PARSIVEL² and automatic weather stations and MICAPS data are used to analyze microphysical parameters of snowflakes in Nanjing in the winter of 2018. The results are as follows. (1) It can be seen that there was a conversion from small snowflakes to large snowflakes when the snowfall intensity in Case 1 increased, while significant increases in the snowflake concentration occurred in the other three processes. The difference in temperature makes the snow formation mechanism in Case 1 different from that in the other three cases, which eventually led to a stable snowfall stage, and the mechanisms for snow intensity increases are different. (2) Gamma distribution and M-P distribution are used to fit different stages of the four snowfalls respectively; the analysis shows that the goodness of fit using the Gamma distribution is higher than that using the M-P distribution at all stages, and the goodness of fit of the snowfall termination stage is lower than that of the initial stage and the entire process of snowfall. The Gamma distributions of the snow particle spectra for the four snowfalls are: N＝107D^-0.21exp(-0.54D), N＝136D^-0.54exp(-0.60D), N＝256D^0.38exp(-1.01D), N＝9.39×10⁴D⁴exp (-7.81D) (N is snowfall particle number concentration and D is snowflake diameter). (3) There are two peaks in the velocity spectrum for Case 1 at about 3 mm, which are close to the frosted and unfrosted curves respectively, indicating that there are two forming mechanisms for the snowfall. (4) Considering Case 1, 2, and 3, the comprehensive Z-I relationship for strong snowfalls during the period of stable stage of the stratiform cloud system in Nanjing is Z＝1708I^1.51.