The invention discloses a wireless power transmission system for online load identification and a load identification method suitable for use in the field of wireless charging. The wireless power transmission system comprises a high-frequency inverter, a primary-side fundamental wave energy transmission module, a primary-side harmonic energy transmission module, a secondary-side energy receiving module, a system load, a secondary-side signal processing and transmitting module, a primary-side signal receiving and processing module and a selector switch. When the system normally outputs power, the selector switch is turned off and is cut off the primary-side harmonic energy transmission module, energy from the primary-side fundamental wave energy transmission module is received through a secondary-side magnetic energy pick-up coil in the secondary-side energy receiving module and transferred to the load; and when dynamic load identification needs to be carried out, the selector switch is turned on and cut in the primary-side harmonic energy transmission module, a fundamental wave in load current of the system and the content and the size of harmonic current are extracted and detected, and an equation set for load resistance and reactance is built according to a superposition theorem, thereby dynamically identifying the property and the size of the load. Load identification is carried out by adopting a harmonic wave, the steps are simple, the energy utilization rate is high, energy transmission of the system is not affected by the load identification process and the load identification accuracy is high.