Accurate transmission line parameters are prerequisites for power system load flow calculations, protection settings and fault location. However, the increasingly compact transmission corridor intensifies electromagnetic coupling between adjacent lines, significantly compromising measurement accuracy. To address this issue, a simulation model of a double-circuit line on the same tower is established using actual engineering data. Systematic analyses quantify the effects of line spacing, coupling section length, transmission power and line arrangement on inter-line coupling strength. The applicability and accuracy of three measurement approaches—the standard guide method, the asymmetric line method and the interference method—are then compared under varied conditions. The findings provide theoretical foundations and practical guidance for interference assessment and method selection in transmission line parameter measurement.