Abstract: In this study, the interaction force between surfactant solution droplets and coal is measured by the mechanical testing device of piezoelectric ceramic double crystal cantilever beam, and the difficulty degree of the droplets wetting coal is characterized. The effects of the concentration of surfactant solution and the type of surfactant on the interaction force were studied. The results showed that in the solution of surfactant fatty alcohol polyoxyethylene ether（9） （AE09） with the concentration of 5×10^-5 mol/L, 8×10^-5 mol/L and 1.5×10^-4mol/L, the solution with the concentration of 1.5×10^-4 mol/L had the lowest maximum repulsive force and the shortest time to reach the maximum repulsive force, so its wetting ability was the strongest. In the solution of three homologous series of nonionic surfactants of polyoxyethylenated fatty alcs（AE07, AE09 and AE012） with the concentration of 1.5×10^-4 mol/L, the maximum repulsive force of AE09 solution was the least, and the time to reach the maximum repulsive force was also the shortest, indicating that it had the strongest wetting ability.