A large amount of W/O emulsions will be formed during reservoir formation and waterflood development，which brings many challenges to chemical flooding for the subsequent enhanced oil recovery. Therefore，the formation theory of crude oil emulsions（W/O，O/W，and W/O/W），the performance variation rules，and the instability behaviors of W/O/W emulsions were studied in detail to clarify the formation rules of multiple crude oil emulsions and their influencing factors. The viscosity increase of W/O emulsions can be divided into two processes with the increase in water content：linear increase and exponential increase. The W/O emulsion emulsified by chemical emulsification forms W/O/W emulsion in oil reservoirs. A higher water content of W/O emulsion indicates a larger droplet size of W/O/W emulsion. Its performance is mainly affected by the droplet size and the percentage of the produced water phase in the W/O emulsion. A stronger ability of the chemical agent to produce the internal water phase of the W/O emulsion means a smaller droplet size of the formed W/O/W emulsion. A higher mole concentration of chemical agents indicates a stronger emulsification ability and a stronger ability to produce the internal water phase. The viscosity of the W/O/ W emulsion is affected by its droplet size，the strength of the interfacial film，and the internal water phase. A lower droplet size means less water phase in the W/O droplet，higher interfacial film strength，and lower viscosity of W/O/W emulsion. The stability of W/O/W emulsion is mainly affected by its droplet size and droplet coalescence rate. The smaller droplet size of the W/O/W emulsion formed by the emulsification of chemical agents means a slower droplet coalescence rate and stronger stability. The initial dehydration rate decreases with the increase in chemical agent concentration. However，as the percentage of the produced water phase intensifies，the final dehydration rate and the time to reach the stable dehydration increase. With the increase in the oil-water ratio，the density of W/O droplets increases，and the initial dehydration rate slows down. In addition，the percentage of the produced water phase in the W/O emulsion decreases with the increase in the oil-water ratio，and the final dehydration rate decreases. As the temperature increases，the initial dehydration speed is accelerated，and the time to reach the stable dehydration stage is shortened. Finally，the final dehydration rate is increased.