A method for correlating data of a terminal device and an apparatus are provided, to correlate data of a single terminal device by a RAN side, and further analyze the data of the terminal device. The method is: A first device obtains first data of a terminal device on a second device, where the first data includes first correlation information, the first correlation information is used to correlate the first data with second data of the terminal device on a first access network device, the second data includes the first correlation information, and there are one or more terminal devices. The first device determines a first identifier of the terminal device, and sends the first correlation information and the first identifier of the terminal device to a second access network device.