Abstract: The outgassing rate of carbon-hydrogen compounds from materials significantly impacts the stability, reliability, and lifespan of precision instruments. Measurement of partial outgassing rate is accomplished through vacuum partial pressure calculations using a quadrupole mass spectrometer (QMS). However, the mass discrimination effect of QMS reduces the measurement sensitivity of high-mass ions, which affects the measurement accuracy of hydrocarbon outgassing rates. Aiming at this problem, this study focused on optimizing and enhancing the apparatus for outgassing rate measurement by orifice conductance method. Additionally, a method utilizing dodecane as a calibration substance for the QMS was proposed to rectify the mass discrimination effect. To verify the effectiveness, the mass discrimination effect of two QMSs was corrected, and samples of PTFE and FKM were selected to test the outgassing rate of hydrocarbons at different times. The results show the method proposed in this paper can effectively reduce the mass discrimination effect of QMS. In addition, the outgassing rate of hydrocarbons in the sample corrected by the mass discrimination effect is significantly higher than that without correction. Among them, the outgassing rates of CxHy-1 and CxHy-2 of PTFE samples increased by 19.78% and 123.83%, respectively, and the outgassing rates of CxHy-1 and CxHy-2 of FKM samples increased by 31.91% and 155.22%, respectively.