The invention relates to a preparation method of a theta-AlF3 micro-nano-spherical catalyst and an application of the theta-AlF3 micro-nano-spherical catalyst to catalytic cracking of 1,1,1,2-tetrafluoroethane for preparation of trifluoroethylene. The preparation method of the theta-AlF3 micro-nano-spherical catalyst comprises the following steps: a fluorine-containing polymer is dissolved in an organic solvent under heating and stirring conditions, then aluminium salt is added to the polymer solution and stirred to be dissolved completely, and a colorless transparent gel-like precursor solution is formed; drying is performed to remove the organic solvent, calcining treatment is performed, and the AlF3 catalyst is obtained. The AlF3 catalyst synthesized with the method has higher catalyticactivity and good stability in a cracking reaction for preparing trifluoroethylene from 1,1,1,2-tetrafluoroethane, the process is simple, a few operation steps are required, the efficiency is high, equipment requirements are low, and repeatability is good.