The invention provides a method for preparing carbonyl fluoride from p-trichloromethylphenyl isocyanate. The method is a new one in which the carbonyl fluoride is safely and effectively obtained by reacting hydrogen fluoride and phenyl isocyanate; and the method can ensure that the reaction proceeds towards the direction of generating the carbonyl fluoride maximally. The method provided by the invention comprises the following steps: in the presence of the phenyl isocyanate and the excessive hydrogen fluoride, performing a first reaction on the hydrogen fluoride and the phenyl isocyanate at a low temperature; performing heating to perform a second reaction; collecting a p-trifluoromethyl aniline product; and performing cooling to collect the liquid hydrogen fluoride, introducing the uncondensed gas into a rectification tower, performing rectification, and performing separation to obtain hydrogen chloride and the carbonyl fluoride. The method provided by the invention can ensure high reaction yield, high product purity, mild reaction conditions and favorable safety; and on the basis of producing the carbonyl fluoride, the hydrogen fluoride, the hydrogen chloride and the p-trifluoromethyl aniline can be produced simultaneously, and no pollutant is discharged, thereby meeting environmental requirements.