The successful applications of two-dimensional (2D) transition metal dichalcogenides highly rely on rational regulation of their electronic properties.The nondestructive and controllable doping strategy is of great importance to implement 2D materials in electronic devices.Herein,we propose a straightforward and effective method to realize controllable n-type doping in WSe2 monolayer by electron beam irradiation.Electrical measurements and photoluminescence (PL) spectra verify the strong n-doping in electron beam-treated WSe2 monolayers.The n-type doping arises from the generation of Se vacancies and the doping degree is precisely controlled by irradiation fluences.Due to the n-doping-induced narrowing of the Schottky barrier,the current of back-gated monolayer WSe2 is enhanced by an order of magnitude and a ～8× increase in the electron filed-effect mobility is observed.Remarkably,it is a moderate method without significant reduction in electrical performance and severe damage to lattice structures even under ultra-high doses of irradiation.