Abstract: The gathering systems in Changqing Oilfield appear scaling problems due to the characters of produced water from multiple strata reservoir. The characters of produced water from different stratas are analyzed, and it is found that the produced water (PW)is of high TSD, high Ca²⁺ and Mg²⁺ contents together with Ba²⁺ and Sr²⁺. According to the analysis results, gathering system operational conditions are simulated by mixed transportation scaling monitor system. The best and worst operational conditions of PW from different stratas have been obtained, which provides an optimization base for the operation of gathering system. The main anti-scale methods include avoiding mixing of incompatible water, controlling physical conditions, using scale inhibitor and optimizing transportation process.