Correlation analysis was used to evaluate the influencing factors and relationship of algae growth and nitrogen and phosphorus concentration in order to determine the algae growth change rule at the mouth of the Jialing River in Chongqing, P. R. China. The results indicate that algae grows rapidly during June and July. Under the same climate conditions and small differences of nutrient concentration, there is a negative correlation between algae cell density and flow velocity. Areas having tranquil water flows are advantageous for algae multiplication. Algae cell density has a positive linear relationship to nitrogen and phosphorus concentrations. Phosphorus has a greater influence weight than nitrogen, however, indicating that phosphorus is the restrictive factor for algae growth．Phosphorus affects algae growth more strongly in areas with tranquil water flows where the algae is more active. Fast flow velocity, abundant sediment content, low water temperature, and other factorss will affect the correlation of algae growth with nitrogen and phosphorus concentrations. This correlation is not obvious during rising flood stages. The results provide important parameters for understanding the changing water quality patterns of the Jialing River and the conditions and mechanism analysis of water eutrophication.