The invention provides a base station spectrum distribution method when a heterogeneous cellular network is networked in the same frequency. The base station spectrum distribution method comprises the following steps: after a microcell base station is added into a heterogeneous cellular network, basic configuration information of a current network of a macro base station cell is read; according to the basic configuration information of the current network, available carrier information in a spectrum pool can be obtained; according to measurement report and graph theories of a mobile terminal connected to the microcell base station, the microcell base station constructs and outwardly broadcasts neighbourhood interference relational graphs itself, and calculates the available carrier number itself according to obtained all neighbourhood interference relational graphs; and the microcell base station selects the available carrier number itself from available carriers in a carrier selection time slot. By means of the spectrum distribution method provided by the invention, distributed and autonomous spectrum distribution of a small cell base station in a heterogeneous network, the network topology of which is dynamically changed, can be realized; therefore, dynamic change of the network topology can be suitable; furthermore, interference in the network is optimized; and mutual interference between adjacent small cells is avoided.