Abstract: In order to improve the effect of water injection in coal seam, to improve the wettability of coal with poor wettability, surfactant was added. Taking the coal samples of Liulong Coal Mine in Baise Group of Guizhou Province as an example, this paper selects four representative and inexpensive surface active agents based on the species of surfactant. By measuring the surface tension of pure water and adding surface active agent and the contact angle with the coal body, the sulfonated sodium bate acid two octyl sodium salt (fast penetrating agent T) was selected as the best surfactant and the best concentration was 0.4%.