In order to obtain high temperature microemulsified acid and provide novel acids for deep acidization of oil and gas fields, a novel high temperature microemulsified hydrochloric acid system with cationic Gemini surfactant propylene-1, 3-bis (octadecyl dimethyl ammonium chloride) (18-3-18) as main emulsifier, n-butanol and n-octanol as assistant emulsifier, diesel as oil phase and hydrocholoric acid as acid phase was prepared in this paper. The thermal stability, phase behavior, retarded reactivity and CaCl2 tolerance of the microemulsified hydrochloric acid were investigated. The results showed that, at proper conditions, cationic Gemini 18-3-18 diesel microemulsified hydrochloric acid may keep stable at 100℃，and CaCl2 tolerance reached 120 g/L. It was proved that the microemulsified hydrochloric acid emulsified by Gemini18-3-18 and AEO9 also possessed good thermal stability at 95℃. It is benefit to enrich the novel high temperature microemulsified acid systems.