In this work, the effects of anionic surfactants on methane hydrate formation were studied. For comparison, three anionic surfactants with the same carbon chain but different head groups, sodium dodecyl sulfonate (SDSN), sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS) were used. SOBS was detected to form micelles under hydrate formation conditions, while SDSN and SDS precipitated before micelles were formed. As a result, concentrations of SDSN and SOS did not show obvious influence on the promotion effect to methane hydrate formation, while the concentration of SOBS significantly affected the promotion effect because of the micelle effect. When SDSN and SDS were used hydrates grew upwards on the reactor wall due to the relatively narrow contact angle of the surfactant solutions on the reactor sidewall, while SDBS led to the hydrates formed mainly in the bottom of the reactor as a result of the relatively wide contact angle. In addition, SDSN and SDS led to much higher growth rate in comparison to SOBS due to the upward growth of hydrates on the reactor sidewall. (C) 2015 Elsevier Ltd. All rights reserved.