The present disclosure relates to terminal devices, access network devices, air interface configuration methods, and wireless communications systems. In one example method, a second access network device in a radio access network determines air interface configuration information of an air interface between a terminal device and the radio access network, and sends a first air interface configuration message comprising the air interface configuration information to a first access network device in the radio access network. The first access network device and the second access network device use different wireless communications standards.