Carbon emission measurement in power systems is an important foundation for clarifying emission responsibilities across different sectors, formulating emission reduction measures, and achieving carbon-neutrality goals. Carbon flow theory, based on the power flow tracking principle, enables the calculation of carbon emission factors and the allocation of carbon emission responsibility within power systems. Since accurate power flow results are fundamental to precise carbon emission factor calculation, their accuracy is affected by the fidelity of the network model. Variations in transmission line parameters may result in significant errors in carbon emission factor computation. To address this issue, a carbon emission factor calculation method considering line parameter correction is proposed. First, the carbon emission factor calculation method based on carbon flow theory is analyzed. Then, by using measurement data and an improved Newton-Raphson method to correct line parameters, a carbon emission factor calculation method that incorporates line parameter correction is developed. Furthermore, the influence of line parameter variations on nodal carbon emission factors is examined. Finally, simulation results verify that the proposed method can effectively improve the accuracy of carbon emission factor calculation.