The invention belongs to the technical field of organic fluorides, and discloses a preparation method and application of fluoroolefin. The method includes: under the catalysis of light, difluoroalkylation-defluorination reaction with ethyl difluoroiodo acetate as a fluorine source is carried out, and aryl benzyl ketonization is utilized to carry out high stereoselectivity synthesis of fluoroolefin. According to the method, ethyl difluoroiodo acetate is used as a fluorine source to prepare the monofluoroolefin compound with high selectivity, so that the production cost can be greatly reduced, and the method has remarkable social benefits and economic benefits. The method is simple in catalytic system, simple and convenient to operate and good in selectivity. A photocatalysis strategy is adopted, and compared with existing metal catalysis, the method is greener and more environmentally friendly. According to the synthesis method, the difluoroalkylation-defluorination reaction taking ethyl difluoroiodo acetate as a fluorine source has relatively high regioselectivity, mild reaction conditions and a wide reaction range, fluoroolefin can be efficiently synthesized, scientific and technological application can be achieved, medicine development is promoted, and the requirements of scientific research are met.