Hydraulic system has extensive applications in national defense industry, aviation, engineering machinery, petrochemical engineering, metallurgical industry and other fields. Reasonable design of the pipes have a significant influence in efficiency, safety and reliability of hydraulic system. Aiming at a common hydraulic system return pipe, an analysis is conducted. Three main factors that impact the pipe pressure loss were considered firstly, which contains loss along the way, partial pressure loss and gravity loss, and the pipe pressure loss was calculated according to theoretical formulas. Then, Fluent was used to analyze the flow characteristics of 90° elbows, T-shape connection pipe and four-way connection pipe in the return pipe, and the speed cloud pictures and pressure distribution cloud pictures of three connection pipe were obtained. The results of simulation provide a basis for the improvement of the design and processing technology of the above three pipe connection pipe, and have a guiding role in the design and optimization of the actual hydraulic system return pipe.