Coke was prepared by coking of coal with addition of Ca-based slag as a catalyst. The solution loss reaction of coke at different temperatures (900~1200℃) was studied in a self-made vertical fixed-bed reactor. The results showed that the solution loss rate of coke remained constant when carbon loss rate (x) was less than 15%, and the solution loss rate gradually decreased at x>15%. The specific surface area of coke after reaction first increased and then decreased, and reached the maximum value at x"15%. Furthermore, the addition of slag improved the solution loss rate of coke, and enhanced its reactivity. A random pore model was used to describe the solution loss reaction of coke, and the activation energy of coke and coke with 1% slag was 132.15 and 103.81 kJ/mol, respectively.