The present invention relates to a stable crystal form, i.e. form A, of 2-tert-butyl-4-methoxyphenol, and to a new preparation method for the 2-tert-butyl-4-methoxyphenol; and the use of the 2-tert-butyl-4-methoxyphenol and the stable crystal form thereof, i.e. form A, in preparing antitumor drugs or immunomodulator drugs. The stable crystal form, i.e. form A, as expressed by a powder X-ray diffraction pattern in an angle of 2θ, using Cu-Kα radiation, has at least 3 absorption peaks selected from the following positions: 6.27±0.10, 6.94±0.10, 12.27±0.10, 13.36±0.10, 14.01±0.10, 14.79±0.10, 15.31±0.10, 17.05±0.10, 18.30±0.10, 19.00±0.10, 20.47±0.10, 20.98±0.10, 22.37±0.10, 23.68±0.10, 24.55±0.10, 25.37±0.10, 30.83±0.10, 33.12±0.10, 40.50±0.10, 42.81±0.10.