The invention provides a state estimation method for the offshore oilfield group power grid. The method comprises the following steps that S1) data collected from SCADA is read in; S2) the initial voltage and current are set, and horizontal and vertical coordinates of a node voltage and horizontal and vertical coordinates of a node injection current serve as quantities of state; S3) the residual error of an objective function is calculated, 2-norm of the residual error of a measurement equation serves as the objective function, and an interior point method is called for solution; and S4) a weighted residual error Tw is used to determine whether a node is an adverse measurement node, if yes, the structure is output, and otherwise, the step 3) is returned to and data of the next node is calculated and determined. The state estimation method has the advantages that the node injection current serves as the quantity of the state, the interior point method is called for solution, the qualified rate of measurement nodes is used to detect and identify adverse data, and the program is high in convergence speed and precision.