Length-biased data widely exist in life research. However, there are relatively few studies on the mean residual life under complete length-biased data. As one of the important indicators to evaluate individuals’survival, mean residual life attracts more and more attention from statistical researchers. In order to construct nonparametric estimations of the mean residual life function under complete length-biased data, two estimations are derived by utilizing the idea of moment estimation. It is proved that the proposed estimations converge in distribution to two zero-mean normal variables under moderate conditions, respectively. In order to evaluate the performance of the proposed estimators in finite samples, a series of numerical simulations are carried out, and the simulation results are compared with those of existing methods. The numerical results show the rationality of two proposed estimations.