Abstract An optimal measurement placement algorithm in the distribution network based on branch-observed is proposed in order to make the distribution network totally observable. Firstly, the observation of the distribution network is analyzed, and the basic optimal model of the measurement placement based on the branch-observed is established. Then an improved model is considered and the measurement placement is more practical. At last, the model has been solved and the correctness of the proposed algorithm has been verified in the 37-bus and 69-bus distribution network.