Water adsorption characteristics and lipid rancidity of fresh and roasted Peanuts were investigated at $25{sim}60^{circ)C$ and $11{sim}85%$ relative humidity. peanuts of 50g were reached to the equilibrium water content in 14 days at $40^{circ}C$, in 30 days at $25^{circ}C$, respectively, in all of the relative humidity. BET monolayer water contents were $2.19{sim}2.69%$ in fresh peanuts and $2.47{sim}2.67%$ in roasted ones as dry basis at $25{sim}40^{circ)C$. Zero order reaction rate of peroxide value(POV) were $8{sim}21times$ lower as $0.032day^{-1}$ and $0.142day^{-1}$in fresh peanuts than those of $0.663day^{-1}$ and $1.120day^{-1}$ in roasted peanuts at water activity of 0.51, but those were showed the relatively smaller differences according to the water activity and temperature. The critical peroxide value(POV) and carbonyl value(CV) were determined as 15.0meq/kg and 4.7meq/kg at $60^{circ}C$ $0.51a_w$ by the regression analysis between chemical and sensory evaluation.