Abstract: Seven typical productivity formulas for branch horizontal well were analyzed in this paper. It was found WANG Weihong formula and LI Dang formula are the two special cases of CHENG Linsong formula, and JIANG Tingxue formula is more accurate than CHENG Linsong formula. Theoretical analysis and case calculation proved that QI Chengwei formula was an important breakthrough in external seepage resistance. Further analysis showed the external seepage resistance made by QI Chengwei is self-compatible and rigorous. Finally, by taking various additional resistances into account, a complete productivity formula was obtained.