Abstract Benzoyl Perfluoro-propenyl Methylene Triphenglarsorance (Ylid-VI) crystal is colourless and transparent. The space group is C2H5-P21/a. The crystal belongs to monoclinic system. The parameters of unit cell are a = 10.365 (8)?, b = 29.106 (4)?, c = 8.630 (8)?, β = 107.20 (28)°. There are four molecules in an unit cell (z = 4). The intensity data were collected on PW-1100 four circle diffraetometer, the total number diffraction amounts to 4966. The Ylid-VI crystal structure has been refined by means of block matrix least square method, R = 0.067.The molecular structure of Ylid-VI indicats that there occurs a eletronic transition between the arsenic atom and the carbon atom in the methene.