Based on the 1958-2007 monthly precipitation data at 4 stations over Tianjin area and the NCEP/NCAR reanalysis data set, the precedent strong influence signal for the anomalous precipitation in rainy season over Tianjin area is investigated by employing the simple correlation and composite analysis. The results show that the annual precipitation over Tianjin area is mainly concentrated in the rainy season. There exists pronounced interannual variability and certain interdecadal variations about the rainfall in rainy season. Additionally, there is a significant negative correlation between the precipitation and NAO in the preceding February. The anomalous NAO in the preceding February has a good potential to be the precedent strong influence signal for the abnormal precipitation over Tianjin area. In the years of weak NAO, the low value systems develop on Tianjin upstream, the South Asia high， the subtropical upper westerly jet and the tropical upper easterly jet lie more northward, and the developments of monsoon depression and trough are noticeable from the Arabian Sea to the Bay of Bengal. The rainfall is likely to be more than normal due to the distribution of the abovementioned synoptic systems. The situations are just opposite in the years of strong NAO.