A large defective troilite (Fe0.9V0.1)0.82S is prepared by a sealed silica-tube method at 800oC and characterized by a powder X-ray diffraction method and using a magnetic property measurement system. The crystal structures of a defective troilite and non defective troilite are analyzed by Rietveld method. The large defect enhances the Fe-Fe pairing and suppresses the waving of Fe-chain along c-direction. The antiferromagnetic property is observed on both troilites. The spin-flip transition temperature of the large defective troilite is 9K.