Regulating spin-related electronic structures of two dimensional (2D) materials by an external electric field plays a substantial role in achieving spintronic and multistate information storage. However, electric-field-dependent ferromagnetic behavior at atomic-thick 2D materials is very difficult to be realized due to their intrinsic inversion symmetry, in which the symmetric spatial distribution of charge density makes it become insensitive to spontaneous polarization from external electric field. Herein, a new-type Janus MnReX3 (X=Se, S) monolayer with noncentrosymmetric configuration in which their orbital hybridization at internal interface can be engineered by rearranging the spatial symmetry of out-of-plane charge density. As a result, the spin exchange interaction among magnetic sites can be regulated by the electric-field-driven charge density redistribution, leading to a controllable ferromagnetic behavior at room temperature. Our results not only suggest a promising strategy to regulate the ferromagnetic response by reducing the crystal symmetry, but also provide a new insight into designing 2D magnetic materials.