The invention relates to a method for reducing the energy consumption of a TD-SCDMA base station system, which comprises the following steps of: respectively acquiring a switching point corresponding to each downlink time slot of a subframe signal, the position of a first symbol of each downlink time slot and antenna carrier path I data and path Q data which are corresponding to a first symbol ofa corresponding position in downlink base band data according to a subframe signal and the downlink base band data which are sent by a local base band unit of a base station system to a remote radio frequency unit; respectively detecting whether corresponding downlink time slots are null service time slots or not according to the antenna carrier path I data and the path Q data; and closing transmitters and launching channels below the null service time slots at the switching points of the null service time slots. The invention can reduce the energy consumption of the whole base station system, save energy source, and prolong the service life of corresponding devices. The invention also provides a system for reducing the energy consumption TD-SCDMA base station system, and null service time slot detection method and device.