Abstract: Smoothing method adopted by world famous stock price averages, such as Dow-Jones stock index, New York Time stock index, removes the impacts of nontransactional variations, but “post-smoothing bias” is occurred in the average. Based on further discussion on methodology of smoothing stock indices, the form, nature and impacts of “post-smoothing bias” was analyzed, re-smoothing method to remove “post-smoothing bias” was raised, and the application of re-smoothing method in the generalized stock indices was discussed.