A big area hail weather occurred in Heilongjiang province in the early spring of 2005, which has been seldom seen in the history, is studied with rada r and other observation data. The analysis is emphasized on the change in struct ure of the echo during the cloud developing, and also the discussion is laid on the relationship between radar reflectivity factor and radial velocity field. Wi th relative low temperature in the spring the convective cloud did not develop h igh and strong, so the usual standards, with which we judge severe weather, do n ot work well in this case. Though the weak echo and no typical hail echo feature have been observed, the characteristic of radial velocity and mesoscale conve rgence and divergence in spring can be found quite clearly. The analysis a nd study of different characteristics between hail weathers taking place in earl y spring and other seasons, are highly significant for better understanding of t he hail echo characteristics in different season.