The invention is suitable for the technical field of communication, and provides an adaptive filter and a filtering method. The adaptive filter comprises a filtering module and a tap coefficient updating module, wherein the filtering module performs time-delay decomposition on an input signal u(n) of a forwarding antenna and generates an error output signal e(n); the tap coefficient updating module acquires a tap coefficient of the next moment according to the error output signal e(n) and adjusts and updates the tap weight of the filter according to the tap coefficient; and a first coefficient updating algorithm control module and a second coefficient updating algorithm control module of the tap coefficient updating module switch operation to solve the problems that when the tap coefficient of the filter is updated, the complicated complex multiplication operation consumes a large amount of hardware resources and the hardware delay is over-long, and simultaneously, the first coefficient updating algorithm control module and the second coefficient updating algorithm control module of the tap coefficient updating module effectively combine the advantages of a 1ms algorithm and an n1ms algorithm to improve the working efficiency and the stability of the adaptive filter.