Abstract: Three types of mesoscale systems developed within 24 hours and caused heavy rainfall of more than 200 mm in a large domain and 469 mm in some local districts of Beijing. Tianjin and Tangshan area during July 29—30, 1975 are presented resectively. They are meso–βscale complex cell, rainbands and meso– scale vortex. In this paper, the features of movement, propagation, development of radar echoes of precipitation and ambient field associated with these systems are analysed. Also, the thermodynamical mechanisms responsible for the systems are briefly discussed