Abstract: The normal sidereal filter is modified,and a way to calculate the mean satellite orbit period by dividing broadcast ephemeris is provided,which is checked through comparison with examples.From the results we can see that,compared to the pre-revision sidereal filter,the modified one can improve the positioning accuracy more efficiently,the accuracy of NEU directions are increased 4.5%,5.2% and 6.2% respectively,and it has better performance between frequencies of 0.001-0.08 Hz.