PURPOSE: To prepare a coal/heavy oil mixed fuel having improved stability, by mixing a dispersion of pulverized coal and heavy oil with water in the presence of a surface active agent.

CONSTITUTION: A coal/heavy oil dispersion is prepared by mixing pulverized coal with heavy oil at high temperature in the absence of water of a surface active agent. The weight ratio of coal/heavy oil is pref. 6/4W3/7. The dispersion is homogeneously mixed with a small amount of water as a stabilizer in the presence of a surface active agent. The amount of the water is pref. 1W10wt%, based on the mixture. The average particle diameter of the pulverized coal is usually ≤100μ, and pref. more than 50% of the coal passes through a 200 mesh sieve.