Abstract: The systematical calculation and analytical research of inhomogeneous degree ( ID ) in common precursor group have been carried out in WYEPTS (Western Yunnan Earthquake Prediction Test Site) and Tengchong Longling seismic areas. It is found that ID anomaly of precursor group is an event of small probability. The average value of anomaly time before earthquake occurrence is about 51 days. There is not a false alarm but only two events failed to predict within 13. 5 year in both seismic areas. The ID anomaly precursor group contains more short term and impending information near the source than the single precursor. It may devel op into a new method of short term earthquake prediction.

Key words: Short term prediction, Inhomogeneous degree of precursor group, WTYEPTS