The stability and phase behavior of acrylamide-based emulsions, prepared with surfactants consisting of lipophilic Span80 and hydrophilic OP10, before or after polymerization were investigated. The research results indicated that the phase separation behavior of the W/O-type emulsions is related to the toluene/water ratio. When the water volume fraction was larger, the phase separation mechanism was mainly a penetration of aqueous molecules from the dispersed-phase droplets. When the water volume fraction was smaller, the phase separation mechanism was mainly a sedimentation of the separated aqueous droplets. At a fixed toluene/ water ratio, the emulsion stability and the emulsion type are related not only to the ratio of the two surfactants but also to the acrylamide concentration, and the effect of increasing acrylamide concentration on the character of the emulsions is similar to that of increasing OP10 mass fraction ( increasing HLB value), which determines the corresponding relationship between acrylamide concentration and HLB value in the most stable emulsion system. To obtain the most stable emulsion at a fixed acrylamide concentration, the emulsion with higher acrylamide concentration needs a lower HLB value for the emulsion systems.