The paper used generalized watershed loading function (GWLF) model to simulate the hydrochemisty process of Lianjiang watershed in the upstream of Xin'anjiang River from 2005 to 2010, and estimated monthly streamflows and fluxes of dissolved nitrogen as well as its source allocation.The result showed that as a valid tool of decision-making,GWLF can effectively estimated the watershed.The Nash-efficiency coefficient of simulation result is above 0.75.From the view of average annual results, the dissolved total nitrogen which amount is transported through surface runoff and groundwater hold 42% and 40% respectively, and has greater relationship with hydrological condition.The high sensitive risk with poor water quality usually occurs in low flow period.The load contributions from septic system (37%) and point source (9%) are significant,which should be particularly paid attention to.The result can provide a reference for the contruction of well-targeted management measures.