There are many zero injection nodes with zero injection power in the actual power grids, and the injection power of zero injection nodes is measured as absolute accurate measurement, but these measurements are not fully utilized. In the state estimation, the result of the first step linear process of the bilinear WLAV state estimation is modified by the zero injection constraint, which not only improves the estimation accuracy, but also does not increase the order of the coefficient matrix, and the improved algorithm still has a higher computational efficiency. Simulation results based on the IEEE standard systems and a real provincial network verify the effectiveness of the proposed method in improving the computation accuracy and computing efficiency.