We study absorbing boundary conditions (ABC) of novel perfectly matched layer (NPML) of three-dimensional truncated magnetized plasma. A modified NPML (M-NPML) method is presented. According to electromagnetic scattering theory of magnetized plasma, we stretch space variables of partial derivatives in Maxwell partial differential equations. In the stretched-scheme complex field splitting form is avoided as truncating ordinary media by PML method. Moreover, the scheme is much easier than uniaxial anisotropy perfectly matched layer (UPML) in programming. Simulation results fit analytical solutions, which shows validity of the M-NPML ABC algorithm.