Introducing a magnetic moment into nonmagnetic two-dimensional semiconducting materials is significant for them in spintronic application. Here, we systematically study the electronic structures and magnetism of 3d transition-metals (TMs) doped two-dimensional (2D) InP3 monolayer (m-InP3) using density functional theory. Our results indicate that all the 3d TMs doping can induce different magnetism (except for Sc), and it mainly originates from the unpaired d electrons filled in the non-bonding orbitals. In particular, Fe doping system obtains the largest total magnetic moment of 5 mu(B). Furthermore, the V, Mn, Co, Ni and Zn doped 2D m-InP3 appear half-metallicity, while Ti, Cr, Fe, Cu doping possess dilute magnetic semiconductor (DMS) property. For the two identical 3d TM atoms doping systems, the ferromagnetic couplings are found in the Ti, V and Fe doping. Remarkably, the largest perpendicular magnetic anisotropy energy (MAE) with 340.38 mu eV is found in the Fe doped system and its physical origin is analyzed by the projected density of states and the d-orbital resolved MAE based on the second-order perturbation theory. These findings provide a promising pathway to realize 2D m-InP3-based materials application in future spintmnic devices.