Abstract: From 2005 to 2006, we spotted monitored stations in Weihai Bay on monthly or quarterly basis for temperature, transparence, pH, dissolved oxygen, chemical oxygen demand, oil content, dissolved inorganic nitrogen, phosphate, etc. The results indicate that average seawater temperature at Weihai Bay is 13.1 ℃, with the highest temperature (25.1 ℃) occurring in August and the lowest (1.1 ℃) occurring in January. Annual transparence ranges from 0.24 m to 5.28 m and pH ranges from 7.56 to 8.45, consistent with the national grade II seawater standard. Dissolved oxygen is within 5.22 ～ 8.09 mg·L^-1, with an annual average of 7.22 mg·L^-1. Chemical oxygen demand is 0.201 ～ 1.531 mg·L^-1 while dissolved inorganic nitrogen is 0.111~0.686 mg·L^-1. Phosphate content fluctuates between 0.016 mg·L^-1 and 0.036 mg·L^-1. In the summer and autumn, EI(Eutrophication Index) is larger than 1, indicating that the main contaminants are dissolved inorganic nitrogen and phosphate. Based on the findings proposals are advanced on marine aquiculture in Weihai Bay.