A method of adaptive full duplex full frequency band echo cancellation comprises the following steps of: carrying out filtration by a sub-band filter, carrying out sub-band echo cancellation by a sub-band echo canceller, carrying out weighted energy analysis and control on system signals, carrying out analysis and detection on double talk active state, carrying out coefficient updating on an echofilter, carrying out nonlinear processing on residual echo, and carrying out synthesis on signals of sub-bands. The method further comprises the step of maintaining reference signal and echo signal tobe synchronous; after the nonlinear processing is carried out, noise reduction, automatic gain control and comfort noise technique can be added. Owing to adoption of the method of echo cancellation,signals are spilt into sub-bands through filtration, thus reducing correlation among signals of sub-bands, improving convergence problem of adaptive filter, reducing data process load of the system, improving processing efficiency of echo cancellation, realizing full duplex of conversation, improving frequency response of communication audio frequency, improving quality of communication and realizing echo cancellation of full frequency band response.