To obtain coke having stably and unfluctuatingly high strength by getting a relation between a temperature of coal after rapid heating and a fractal dimension at the surface of a pore and setting a hot forming temperature based on the relation.

There is provided a process for pretreating coal for a coke oven wherein coal is rapidly heated and subsequently is subjected to hot forming, and preferably the hot forming temperature is decided based on the temperature where the value of the fractal dimension at the surface of pores of coal is smallest. The why reason is as mentioned below. Rapid heating of coal generates rapidly a plasticized portion to effect increase of coking property. However, too high a temperature after heating causes semi-coking of the plasticized portion resulting in loss of coking property. The fractal dimension at the surface of pores indicates unevenness of the surface. When plasticized portion is formed by rapid heating, the portion fills the pores causing decrease of the fractal dimension at the surface of pores. The lower the dimension is, the more plasticized portion is formed, namely, the more coking component of coal is formed.