The influence of cation-mixing on photo luminescence(PL) of PbI2-based organic/inorganic perovskite thin films expressed by chemical formula (C6H9C2H4NH3)(2)PbI4 was investigated. Cation-mixing to inorganic layer by addition of ZnI2 or CdI2 did not affect the character of exciton in the films because all optical spectra of the (CRE)(2)(Pb,M)I-4 films were the same profile. Dependence of PL intensity at 2.4 eV of photon energy(PL2.4) on inorganic layer compositions was changed by kind of additive cation. In the case of Zn addition, PL2.4 was uniformly decreased with an increase of additive amounts of Zn. On the other hand, PL2.4 of the (C6H9C2H4NH3)(2)(Pb,Cd)I-4 films remarkably increased with increasing of Cd concentration up to 20 mol% Cd. It was obvious that cation-mixing with Cd is effective to advance the optical properties of the (C6H9C2H4NH3)(2)PbI4 films. Relationships between PL2.4 and layer or the films were discussed according to structural analysis using XRD.