Embodiments of the invention provide a carrier aggregation function activation method and device. The method can be used for activating a carrier aggregation function in a heterogeneous network and comprises: acquiring a first user access number of a macro base station and a second user access number of a micro base station; determining whether the first user access number is over a first threshold and the second user access number is over a second threshold; if the first user access number is not over the first threshold and the second user access number is not over the second threshold, determining a concentration ratio of users in a coverage range of the micro base station, and determining whether the concentration ratio is over the second threshold; and if the concentration ratio is over the second threshold, activating the carrier aggregation function. The carrier aggregation function activation method and device provided by the embodiments of the invention can self-adaptively select whether to activate the carrier aggregation function according to network situations.