This study reports, for the first time, the second-harmonic generation (SHG) property of Pb7F12Cl2 as a promising infrared nonlinear optical (NLO) material. Powder second-harmonic generation (SHG) indicates that the compound exhibits phase-matchable SHG properties, which are 1.6 times stronger than those of KH2PO4 (KDP). The infrared transmission range could reach 20 μm. The UV absorption indicated that the band gap was about 4.5 eV. A preliminary measurement of laser damage threshold (LDT) is about 80 MW cm-2, which is much higher than AgGaS2 (currently commercialized IR NLO material, 5.2 MW cm-2, measured in the same condition), indicating that Pb7F12Cl2 is a potential IR NLO material with high LDT. Theoretical calculations were also performed to elucidate its band structure, electronic configuration and second-order nonlinear coefficients. Particularly, the distinct role of different Pb atoms located in divergent coordinations has also been elaborated using orbital analysis.