Based on the T63 model data,the torrential rainfall over Hebei province during August 1996 (‘96.8’event) was analysed by filtering low layer stream field.The results are as follows:within the east-north quadrant of Typhoon 9608 low,there was a convergence line whose moving trend was northeast to southwest.It resulted from the interaction of the typhoon low air pressure and the cold air in the westerly wind bnad,while the former was moving northward.Its life period extremely coincided with the heavy rain's,so it was one of the meso-scale synthetic system that caused ‘96.8’event.The convergence line had some features of an easterly wave,and extreme rainfall zone appeared at the east-south side of the convergence line.