Abstract: According to the abundant obsexsrved data from the Tangshan earthquake, by unified anomaly identification method and a new research train of thought, the precursory characteristics of radon before the Tangshan earthquake have been resiudied.The research result shows that the time distribution of radon precursors before the Tangshan earthquake showed a whole charatenristic, stage characteristic,acceleration characteristic;the space distribution showed a network characteristic and belt characteristic.Furthermore, the relationship between the mechanism of radon anomaly and seismogenic process has been explained in physics.