Six dendrimers with the same polyamidoamine (PAMAM) basic structure but different terminals/generations were synthesized by divergent method. The dendrimers were studied by surface, tension measurement at the air-water interface. The demulsification performance for oil/water (O/W) simulated crude oil emulsion and crude oil extract directly from field was investigated. The experimental results indicate that the three dendrimers. terminated with ester groups were insufficient demulsifiers for crude oil emulsion. However, the three dendrimers terminated with amine groups exhibited excellent demulsification performance for O/W emulsions. As demulisifers, amine based dendrimers; were superior to the commercial polyether ones (SP-169 and BP-169). The possible mechanisms for the nanocontainer effects of the dendrimers, through either surface adsorption or internal encapsulation, were discussed.