A wireless power transfer system based on magnetically coupled two resonators is analysed using the filter theory. Design equations for each lumped parameter circuit components are derived. As a result, change of coupling coefficient between the resonators and/or change of load resistance are easily responded. Effect of circuit loss to the design theory is also addressed. After designing a power transfer system, a real system is constructed using spiral and loop coils. Dependence of circuit elements on their dimensions is measured in advance and used to cope with the designed element values. Simulated response by use of designed element values and measured result are compared, indicating the validity of the theory.