The Magnetically-coupled resonant (MCR)technology is exploited in this paper to realize Synchronouswireless information and power transfer (SWIPT) function,which means that the power carriers also transmitinformation. The circuit structure of SWIPT system is analyzedand the existence of two optimal frequencies in powerefficiency under small resistance circumstance is proved.The physical parameters having influences on the two optimalfrequencies are discussed, such as the distance betweencoils, impedance characteristics of coils and loads.These results provide a way to increase the bandwidth ofMCR technology, while maintaining high power efficiencyto realize SWIPT function. Simulations and experimentalresults are presented to verify the feasibility of the proposedsystem and obtained theoretical expressions.