An L0-norm constrained improved proportional normalized least-mean-square （L0-IPNLMS） algorithm based on set membership filtering （SMF） theory （SM-L0-IPNLMS） is proposed to effectively reduce the computational complexity of echo cancellation algorithms in digital hearing aids. The variable step size theory of set membership （SM） is introduced into the L0-IPNLMS algorithm to achieve a faster convergence speed in the proposed algorithm. Moreover， by updating the filter coefficients selectively under the bounded error margin， unnecessary iterations are reduced and then the power consumption of the digital hearing aids are decreased. Experiments demonstrate that compared to the L0-IPNLMS algorithm， the computation of the new algorithm is reduced by 15.3%. In the situation that random signal and real speech are input respectively， the convergence speed is improved by 28% and 32.8%， the misalignment is reduced by 1 dB and 3 dB， the mean square error is reduced by 0.66 dB and 1.68 dB， the echo loss enhancement is improved by 0.7 dB and 1.79 dB correspondingly. Furthermore， the SM-L0-IPNLMS algorithm is greatly robust for the input conditions of low SNRs.