The invention, which belongs to the DC / 
DC converter field, discloses a 
power transmission method and device of a bidirectional 
wireless electric energy transmission system. The method comprises stepsof maintaining a 
switching frequency of a first full-bridge converter unchanged and reducing a 
switching frequency of a second full-bridge converter under a 
light load condition, collecting a currentoutput 
signal of the first full-bridge converter, subtracting the current output 
signal from a set value, performing PI control, and normalizing the current output 
signal into an 
internal phase shiftangle beta2 of the first full-bridge converter, calculating a fundamental wave phase shift 
phase angle delta of the first full-bridge converter and an 
internal phase shift angle beta1 of the second full-bridge converter through a ZVS 
soft switching condition function and an efficiency optimization function based on beta2, updating parameters in the 
digital processor of the first full-bridge converter according to beta2 and 
delta, and updating parameters in the 
digital processor of the second full-bridge converter according to beta1, so that the first full-bridge converter and the second full-bridge converter respectively output symmetrical square 
waves with the pulse widths of beta2 and beta1, and the component 
phase difference of the corresponding frequencies of the two symmetrical squarewaves is 
delta. ZVS 
soft switching is easier to realize, and the 
system transmission efficiency is improved.