Visual observation of HCFC141b gas hydrate growth process outside of a horizontal heat transfer tube was done on a visual apparatus of gas hydrate reaction system. Growth processes of two situations (with, or without sodium dodecyl sulfate (SDS)) were observed, their growth morphology were compared and explained with the theory of surface free energy. During the experiment process, phenomenon of gas hydrate fast nucleation from melting ice was found and explained with Zhou V Sloan's hypothesis qualitatively. From the experiment results, it was found that gas hydrate formed in the liquid HCFC141b phase along the heat transfer tube in a system with SDS (SDS water solution-liquid HCFC141b system), while along the glass in a system without SDS (distilled water-liquid HCFC141b system), so the formation heat of gas hydrate can be absorbed more quickly in a system with SDS than in a system without SDS, which lead to a more quick growth rate. According to the above research, some suggestions were presented on the designation of heat exchanger and reaction materials for the gas hydrate indirect-contact cool storage system. (c) 2004 Elsevier B.V. All rights reserved.