Abstract: An unstructured numerical algorithm of Roe's second-order upwind is proposed to solve the 2D tidal in the sea field of the Shengli oilfield.In order to make the Roe format practiable in the calculation under complicated geography condition,the Ropers method is used to deal with the term of bed slope source in the equation,so that the flux can be balanced.The method of step by step is used to calculate the friction source terms and enhance the stability of calculation.The mathematical model is successfully used to the Shengli oilfield waters,and gets better results.