Abstract: In order to improve the calculation speed and precision for bending moment distribution method calculation, the process of bending moment distribution was transfered as sequences of geometric series. After the first round of the bending moment distribution and transfer, first item and common ratio of the sequences of geometric series can be found, and by using the geometric series formula, the exact solution can be got simply and accurately. This paper brought up the idea of using bi-direction transmission and geometric series to seek the exact solutions of structures which have three distribution points during the procedure of the bending moment distribution method. The accuracy and the practicality of the proposed method were verified by a computation example, which is a two-span asymmetric frame under asymmetric load. The solutions of both computer analysis and formula method computation were compared.