The process of snow melting and the size distribution function of hydrometeors near the melting layer are described. The size distribution of snow, collapsed snow and raindrop can be fitted in with the expression of N=N0exp(-λD) near the melting layer, the spectral parameters N0 and λ are related to temperature, the relation between N0 and λ, can be fitted in with the expression of N0 =σλβ, parameter β is determined by hydrometeors