A crystal form of a deuterated AZD9291 has an X-ray powder diffraction measured using Cu-Kα rays with diffraction peaks at 7.1±0.2, 8.5±0.2, 9.4±0.2, 10.3±0.2, 15.1±0.2, 16.3±0.2, 18.7±0.2, 22.0±0.2, 25.6±0.2, and 26.0±0.2. The crystal form of the deuterated AZD9291 is used in the preparation of medicaments for the treatment of cancer. The crystal form of the deuterated AZD9291 provided by the present invention has stable physical and chemical properties and good metabolic stability, and blood concentrations in vivo and concentrations in the brain thereof are significantly improved, achieving an improved therapeutic effect.