This paper deals with the anomalous features of crust stress change, based on the data observed at Changzhi and Daixian crust stress stations in Shanxi province before the Datong-Yanggao Ms6.1 earthquake. There are not only tendency anomalies, but also short term imminent anomalies. The general tendency is:decline-unbiased-rising. The author made a more accurate short-term prediction before the earthquake, based on the anomalous change of crust stress.