Abstract: During fracturing treatment of oil production wells with viscous crude and crude oil of high freezing point,it is suggested to adopt in-situ heat fracturing liquids to avoid the cold damage to formation by injecting cold fluid.In-situ heat fracturing liquids are made based on common water-base fracturing liquids,with some NaNO2,NH4Cl and HCl added into the base fluid.When the additives are mixed and react,much heat will give out.A mathematical model of wellbore temperature profiles during in-situ heat fracturing treatment based on heat-balance equation is established in this paper,and a computing software was developed.Finally based on a case history of Liaohe oilfield,the effect of surface injection temperature,injection rate and concentration of catalytic agent on concentration of heat-generation agents was investigated by means of orthogonalizing design technique,and developed optimization methods on concentration of heat-generation agents in insitu heat fracturing treatment.