Rhodium-catalyzed cycloaddition reactions are a powerful tool for the construction of polycyclic compounds. Experimental combined with DFT studies were used to investigate the temperature-controlled chemoselectivity of cationic rhodium-catalyzed intramolecular cycloaddition reactions of ene-vinylidenecyclopropanes. After a series of mechanistic studies, it was found that trace amount of water in the reaction system play an important role for generating endo-double bond product and revealed that trace amount of water in the reaction system including the rhodium catalyst, substrate and solvent were enough to promote the formation of endo-double bond product, and additional water could not further accelerate the reaction. DFT calculation results show that the addition of water indeed significantly lowers the energy barrier of proton transfer step, making the formation of endo-double bond product more likely to occur and confirmed the rationality of water-assisted proton transfer occurring in the selective access to endo-double bond product.