The invention relates to a method and device for measuring a surface temperature of a high-speed rotary crystallizer. The method comprises the following steps of: before spraying a belt, respectively measuring a first temperature and a second temperature; during spraying the belt, controlling the contact degree of a thermocouple head and the crystallizer to be constant according to the swelling increment generated by the deformation of the crystallizer due to thermal shock of molten steel, and measuring a third temperature; and figuring out the surface temperature of the crystallizer during spraying the belt according to the first temperature, the second temperature and the third temperature. According to the invention, the contact degree of the thermocouple head and the crystallizer is controlled to be constant, the situation that different degrees of friction temperature raising are caused by inconsistent contact degree of the thermocouple head and the crystallizer can be avoided, and the contact temperature measurement can be realized. The device has the advantages of low cost, convenience, rapidness, reliability, relative simpleness in maintenance, and the like.