Abstract: Bullheading can kill well and establish well control for those wells with sulphur gas when conventional well kill method is not suitable.The establishment of bullheading killing model to calculate the parameters and analysis of surface casing pressure in bullheading process can help the successful implementation of bullheading.On the basis of analysis of bullheading killing adaptability,a bullheading killing parameter calculation model and wellhead casing pressure calculation method were built as well as the analysis of effects of gas volume and killing fluid in the wellbore on the maximum casing pressure.The results show that it is suitable to use bullheading when reservoir permeability is over 30 mD,short open-hole and wellhead with high pressure bearing capacity.The larger volume of gas within the wellbore in the process of bullheading,the higher wellhead casing pressure would be.The higher the killing fluid discharge,the greater the friction and the higher the pressure needed for oil and gas to enter into reservoir.The calculation results provide theoretical support for the field application of bullheading.