The work aims to explore the special feed mode and flow channel to meet the special demand for long round hollow flow balancing. Fluid mechanics was used to analyze the flow of LDPE resin and study the relationship between the forming quality of long hollow cylinder and the number and gap of die flow channel so as to finalize the best number and gap of die flow channel and verify the accuracy of the analysis data by trial results. When 1 coat-hanger channel (2 inlets) and 6 slit channels (4, 3, 3.5, 1, 5 and 1 mm) were adopted, the forming quality of long hollow cylinder was the best:uniform wall thickness with deviation less than 0.15 mm, smooth outer surface without wrinkles and lines and good verticality with skewness less than 3 mm. The proposed design scheme is advanced and effective, which can be used to form long hollow cylinder in the production of LDPE plastic bottle for packaging.