Magnetic resonance electrical properties tomography (MR-EPT) is an emerging technology which plays an important role in specific absorption rate monitoring. The current integral-equation (IE) based MR-EPT methods utilize simulated incident radio-frequency (RF) fields, which are inaccurate and lead to reconstruction errors. In this work, the incident field approximation (IFA) is first demonstrated. IFA utilizes a reference subject and RF field mapping techniques to map the incident field, hence the loading effect of the RF coil can be involved in the IE-based MR-EPT. This method may push the IE-based MR-EPT into practical utilization at UHF-MRI systems.