By means of the first-principles coherent potential approximation within the KKR method, we have investigated the magnetism and electronic structure of Mn-doped YCrO3. Compared with undoped YCrO3, the Mn-doped YCrO3 has an enhancement of magnetic moment value, which is likely to originate from carrier-mediated exchange of the half-metallic semiconductor. Total energy calculations show that for doping concentrations (5, 10, and 15 %), ferromagnetic state is more favorable than the ferrimagnetism state, while for YCrO3 with a high doping of Mn (20 %) has a stable ferrimagnetic ground state and the total magnetic moment weakens. The calculated magnetic moment of YCrO3 doped with Mn mainly originates from transition metal Mn and Cr atoms with a little contribution from O atoms due to the hybridization between 3d electrons and O 2p electrons. Electronic structure indicates that Mn-doped YCrO3 shows a half-metallic behavior. Our results could be potentially useful to design a promising dilute magnetic semiconductor for the applications in the field of spintronics.