The main objective of this work is to study the sensivity of pristine, Al, P and Al & P doped Ga12N12 to adsorb phosgene (COCl2) molecule. The interaction of COCl2 from O, C and Cl sites on the surface of Ga12N12 is investigated by applying the density functional theory (DFT) at the cam-B3LYP/6-31G(d) level of theory. The geometrical and electrical structures, quantum descriptive, thermodynamic parameters, solvent effect, atom in molecule theory (AIM), natural bond orbital (NBO), and the reduced density gradient (RDG) are calculated at the above level of theory. The calculated results indicate that the adsorption of COCl2 on the surface of pristine and Al, P and Al & P doped Ga12N12 is exothermic, as well as Al-doped Ga12N12 is more favorable than P and Al & P doped. The recovery time results for adsorption of COCl2 from O site on the surface of Ga12N12, Al-Ga11N12, Ga12N11P and Al-Ga11N11P are 0.103, 4.69×10 -7 , 3.81×10 -12 and 4.31×10 -7 respectively. As a result, these nanoclusters can be used as sensor devices toward COCl2 molecule. The deformation energy results reveal that the structural change of Ga12N12 and COCl2 at all adsorption states are not significant. The AIM, RDG and NBO results demonstrate that the intermolecular interaction from O site of COCl2 on the surface of pristine, Al, P and Al & P doped Ga12N12 is stronger than C and Cl atoms sites of COCl2 as it is an electrostatic attractive type.