Abstract: In order to increase the success ratio of sidetracking branch horizontal well in partial buried-hill superhard limestone strata of Liaohe Oilfield and deal with the high construction difficulty, this paper carried out a series of studies on sidetracking efficiency and reentry evaluation. After a model for calculating the sidetracking efficiency was established, the bottom hole drilling tools and construction process suitable for sidetracking were selected by analyzing the sidetracking efficiency of bottom hole assembly (BHA). Then, a model for calculating the string reentry difficulty coefficient was established. Whether a string can run into the main hole smoothly can be prejudged in advance by analyzing the string difficulty coefficient in running into the main hole, so as to prepare the countermeasures in advance to improve sidetracking efficiency and success ratio.