Embodiments of the present disclosure disclose a data transmission method which includes: sending, by an REC, a first part of downlink data of a downlink period to an RE before the downlink period arrives; sending, by the REC, a second part of the downlink data of the downlink period to the RE in the downlink period, where the second part and the first part constitute all downlink data of the downlink period; receiving, by the RE, the first part and the second part of the downlink data of the downlink period; and sending, by the RE, the first part and the second part as the downlink data through an air interface in the downlink period. Accordingly, the embodiments of the present disclosure also disclose a base station which can effectively improve utilization of transmission bandwidth of a CPRI interface and utilization of spectrum resources of the air interface.