In single-observer passive location the performance of the Unscented Kalman Filter (UKF) using Unscented Transform (UT) is better than that of Extend Kalman Filter (EKF) and its derivative algorithms. But UKF has more amount of computation. To solve the problem an improved filter algorithm based on Schmidt orthogonal transform was proposed. The algorithm followed the selection criterion for sampling point and used Schmidt orthogonal transform sampling strategy to reduce the number of sampling points. The algorithm was applied in passive locating of a moving emitter. The computer simulation results show that the algorithm can reduce the computation cost and improve the calculation efficiency while keeping a satisfactory filtering precision.