The invention relates to a cell base station scope expansion and base station selection method based on a signal to noise ratio. The method comprises steps that, S01, a macro base station-picocell base station heterogeneous network model is established; S02, the k is made to be 1; S03, in the kth sector, all users respectively feedback RSRP data through an uplink link to a macro base station and a picocell base station in the kth sector; S04, SINR data of each user belonging to different base stations are calculated by the macro base station and the picocell base station in the kth sector; S05, an alternative bias value is set for the picocell base station in the kth sector; and S06, each user in the kth sector respectively establishes connection with one base station, if the k is smaller than the s, the k is made to plus 1, returning to the step S03 is carried out, if the k is equal to the s, base station scope expansion and base station selection of all sectors are accomplished. Compared with the prior art, base station selection is flexible for the users, communication pressure of the macro base station is alleviated, the lowest signal to noise ratio is guaranteed for the users, and average throughput of the users is improved.