Abstract: The characteristics of the moving course of Typhoon Matsa (No.0509),associated heavy rain and physical quantities fields have been analyzed,with focus on the reason of the typhoon's abrupt northeastward turn in Anhui Province and heavy rain concentrating in the northeast of typhoon center instead of near it. Meaningful conclusions are as follows. The reasons of typhoon abrupt turning are that the subtropical high pressure was moving southward and divergence fields of 200hPa were to the right of the typhoon center; there was no obvious cold air invading Shandong after the typhoon entered the westerly belt; the southeasterly jet of typhoon and shear brought heavy rainfall to the Shandong peninsula before the typhoon entered Shandong. But after the typhoon's movement into Shandong,the typhoon's inverted trough brought the rainfall to the northern and central Shandong.