Abstract: Analysing the radon data from several wells in Beijing-Tianjin region, it is believed that the main characteristics of radon anomalous field in this region before the Tangshan earthquake are as follows:1) There was a trend anomaly of the regional average variations in radon for nearly four years, and the anomalous duration was closely related to the Tangshan earthquake (including strong aftershocks). 2) The moderate-term anomaly of radon (1975.8-1976.4) showed a radiative transmission phenomenon from the epicentre to the surface at a speed of 35km/month.3) Just before the Tangshan earthquake (some smaller shocks had occurred in early July, 1976), the sharp radon variations showed itself an opposite pattern, converging from the surroundings towards the epicentre at a speed of about 25-30km/day.The characteristics mentioned above are discussed on the basis of premonitory creep together with the results of simulation tests. It is presumed that if the linear strain reachs 10^-6-10^-5 in the study region, the anomalous variations in radon can be observed distinctly.