Abstract: Reducing rivers nitrogen and phosphorus is an important method that can control the lakes nitrogen and phosphorus pollution. In order to explore the spatial and temporal variations of rivers nitrogen and phosphorus reduction rates around the Lake Taihu, total nitrogen(TN) and total phosphorus(TP) absolute reduction rates(Ra) and relative reduction rates(Rr) were measured through selfdeveloped insitu devices in the inlet rivers around west Lake Taihu in four seasons between 2014 and 2016. The TNRa of northwest and west rivers in summer or autumn were higher than those in spring or winter, and theTNRa of south rivers in autumn or winter were higher than those in spring or summer. In the summer the TNRa and TPRa of northwest and west rivers were significantly higher than that southwest rivers, and the rates of south rivers in winter were significantly higher than others (P<0.05). The rivers spatiotemporal TNRa differences were affected by particalate total nitrogen (PTN) and the seasonal water temperatures. The seasonal TPRa difference of was caused by seasonal difference of TP concentrations. The main reasons that affect season TPRa were various. The spring main factors were water physical properties such as pH, and the summer factor were TP and suspended solids; whereas the main autumn and winter factors were only suspended solids and TP, respectively. Those Lake Taihu rivers TNRr and TPRr were affected by TNRa and TPRa and its initial TN and TP concentration.