This paper presents an inductively coupled power transfer (ICPT) system that can transfer energy with high efficient from primary side to secondary side with variable load from 50 to 300 Ω via electromagnetic resonant coupling and output stable voltage. Main reasons for low efficiency for wide frequency deviation have been investigated. Typical compensation structures are compared in terms of efficiency, and load range. The series-parallel compensation framework is adopted to keep both side coils work in resonant condition and output maximum voltage. A practical ICPT prototype was conducted and the performance with different compensation networks were compared experimentally. Simulation and experimental results are illustrated to show the stability and effectiveness of this inductively coupled transfer system.