Abstract: Based on the investigation in Maowei Sea area in July， 2018， concentrations of urea and different forms of dissolved nitrogen in surface seawater were determined with diacetyl monoximesemicarbazide hydrochloride method and spectrophotometric method. The concentration variations and distribution characteristics of urea and the components of dissolved nitrogen are studied. The source and influencing factors of urea are also discussed. The results show that the concentration of urea （calculated as nitrogen） in Maowei Sea in the summer ranges from 0.40 to 1.13 μmol/dm³ with an average of (0.51±0.18) μmol/dm³. In the study area， the average concentration of urea in the Qinjiang estuary is higher than that in Maolingjiang estuary. Urea accounts for 0.8%-10.3% of the dissolved organic nitrogen （DON） in Maowei Sea. The concentration of urea in the study area gradually decreases from the estuaries to open waters. High urea concentrations are located in waters near the river mouths. It shows that terrestrial input and biogeochemical process in the sea are the main factors controlling the urea distribution．