In the present paper, we address the influence of dilute charged impurity, the perpendicular electric field, and the perpendicular magnetic field on the electronic density of states (DOS) of phosphorene. This is done with the help of the continuum model Hamiltonian and the Green's function approach. Also, the magneto-electron-impurity interaction effect is carried out within the full self-consistent Born approximation for the small density of impurities. We observe a semiconductor-to-semimetal phase transition in both armchair and zigzag directions when the system is unbiased and infected by impurity atoms at strong magnetic fields, whereas there is no phase transition in biased case. Moreover, both impurity concentration and impurity scattering potential parameters lead to the decrease of the band gap. Further, these parameters play different roles in the degeneration of the midgap states-induced of unbiased and biased phosphorene in the presence of a magnetic field. Our findings improve the ability of experimentalists in controlling electronic and optical properties of phosphorene.