Formation and reformation of methane hydrate in (water + diesel oil + sorbitan monolaurate) dispersed systems have been investigated to test the memory effect using particle video microscope and focused beam reflectance measurement probes. The factors which would affect methane hydrate formation, the dosage of sorbitan monolaurate, water cut, and initial experimental temperature, were examined. The results show that there exists obvious memory effect when methane hydrate reformed in water/diesel oil dispersed systems at initial temperature near methane hydrate formation zone, even maintaining at the initial temperature for 168 h after methane hydrate dissociation. The subcooling will increase with prolonging of maintaining time, which suggesting that memory effect would disappear if time is long enough. When initial temperature increases to 5 K higher than the equilibrium value, the subcooling of reformation of methane hydrate is similar to that of hydrate first formation, which implying that memory effect disappears.