Abstract: In this paper, the mathematical model of anthracite dehydration was established through the study of the migration path and the change law of the anthracite coal under the effect of isothermal drying. The 0.2 to 0.25 mm anthracite coal was designed and the water loss test was carried out under the conditions of 75 ℃ and 105 ℃, respectively. The water loss rate fitting curve for coal sample with 0.20 to 0.25 mm particle diameter in X_c1<X< X_c2 stage under different temperature conditions is obtained. The experiment has measured the same size coal samples, and the water loss rate v and temperature T in X_c1<X<X_c2 stage have two polynomial relations, the relation satisfies v=-0.000 3T²+0.062T-2.444 4, the correlation coefficient is R²=0.902. The formula shows that the increase of temperature in the same size coal sample below 90 ℃ can significantly accelerate the coal sample losing water speed. When the drying temperature increased to about 90 ℃ above 0.47 mm, the rate of water loss did not increase significantly with the increase of temperature.