Abstract: Confluence and distribution of multi-branch pipeline （CDMBP） can effectively reduce pipeline density and improve space utilization，but unreasonable structural design can easily cause too much pressure loss and excessive flow distribution difference.A numerical method for the optimal design about CDMBP is proposed in this paper.The paper studies the influence law of multiple parameters，including Reynolds number，outlet and inlet area ratio，closed cavity length at the end of the common chamber，branch pipe spacing and the number of branch pipes，on the flow distribution and pressure loss with parametric analysis.The results show that：there is a pre-ssure recovery zone in the confluence and diversion cavity，which has an impact on the flow distribution and pre-ssure loss of each branch; the Reynolds number has an impact on the flow distribution; the increase of the Reynolds number may increase the pressure loss and the difference of flow distribution; the influence of flow distribution and pressure loss from the length of the end common chamber is negligible; the outlet and inlet area ratio，branch pipe spacing，and the number of branch pipes are importantly related to flow distribution and pressure loss.These factors need to be comprehensively considered in the optimization design of the pipeline structure.These results can be used to guide the optimal design of the CDMBP.

Key words: confluence and distribution, multi-branch pipeline, flow distribution, pressure loss