The application provides a noise power estimation method and device. The method comprises the steps of obtaining a power postponed spectrum corresponding to a time slot 0 in a present subframe and a power postponed spectrum corresponding to a time slot 1; obtaining a present estimation interval set corresponding to the present subframe; targeted at each estimation interval, obtaining a plurality of power points at a same position; executing a second-order algorithm on the plurality of power points of the time slot 0 and the time slot 1 to obtain the noise power of the estimation intervals; and the mean value of the estimation interval is determined to be the noise power of the present sunframe. In the computational process of the application, signal power is eliminated except noise signal power. Consequently, the noise power can be accurately computed through adoption of the application, so that further improvement of an LTE-A system can be realized through utilization of the noise power.