Abstract: Influence factors to the on-lin calibration process of Coriolis Mass Fl0wmeter (CMS) in Lanzhou-Chengdu-Chongqing Products Oil Pipeline.The Influence factors inlude the influence of flow, the influenceof pressure, the influence of damping coefficient and the times of piston running of commpact proverinfluencing on the testing repetition.This paper gives the formulas used to calculate the volume of theliquid which goes through provers actually and the testing of CMS by prover.In is pointed out that theproblem needed to pay attention to that CMS is tested on the pipeline by prover with vibration tubedensimeter.