In order to improve the temperature resistance of emulsifier for oil-based drilling fluid，main emulsifier（PF-EMUL HT） and auxiliary emulsifier（PF-COAT HT）were prepared by using vegetable oleic acid，diethylenetriamine and maleic anhydride. The molecular structure and temperature resistance of two emulsifiers were characterized by infrared spectrometry and thermogravimetric analysis. The emulsifying ability and temperature resistance of two emulsifiers were analyzed by measuring the dynamic interfacial tension，emulsification efficiency and electrical stability of the emulsion. The possible emulsification mechanism was also proposed. At the same time，the influences of emulsifier dosage，oil-water ratio，temperature and density on the performance of drilling fluid were studied. The results showed that PF-EMUL HT had amidation group，while PF-COAT HT had multi-functional groups，such as amido group and carboxyl group. These two emulsifiers could effectively reduce the interfacial tension between oil and water. The demulsification voltage of the emulsion prepared by the two emulsifiers was more than 370 V. The emulsification efficiency was 96% after aged at 232 ℃. The oil-based drilling fluid had favorable stability after aged under the conditions of 150—232 ℃ and 60:40—90:10 oil-water ratio，which could satisfy the operation needs of high temperature and high pressure well and directional well.