The invention discloses a preparation method of a coloured chalk. The preparation method comprises the following steps: (1), providing roots, stems or leaves of edible plants and edible petals or fruits having colours; (2), respectively drying the roots, stems or leaves of the edible plants and the edible petals or fruits having colours so as to obtain a main raw material and a dyeing raw material; (3), respectively crushing the main raw material and the dyeing raw material so as to obtain main raw material powder and dyeing raw material powder; (4), steaming the main raw material powder and the dyeing raw material powder; (5), mixing the steamed main raw material powder and dyeing raw material powder so as to obtain a mixture; and (6), forming the mixture so as to obtain the coloured chalk. According to the preparation method of the coloured chalk provided in the embodiment of the invention, the realistic problems that the traditional chalks are harmful to physical and psychological health of teachers and students and have pollution to the environment and the like can be solved.