The invention belongs to the fields of medical evaluation, detection technology and experimental zoology, and specifically relates to a construction method of animal model of rat which is used for screening medicaments for treating chronic inflammation, and evaluating methods for treating systematic chronic inflammation. The method comprises the following step that healthy male SD rats are administered with lipopolysaccharide by tail intravenous injection, on an every first day of a week for 4-8 weeks persistently, at a dosage of 120-300 [mu]g per kg of body weight, so that pathologic changes, which meet pathological characteristics of chronic inflammation, mainly of an increased ratio of peripheral blood leucocyte count to neutrophile granulocyte, an increased serum hypersensitive C-creative protein level, infiltration of heart, liver, lung, kidney in inflammatory cells, and haemostasis and oedema of tissues are generated. The method has a good repeatability, and operation of the method is simple, easily controllable and mechanism-clear, besides indexes can be analyzed quantitatively and are convenient for statistics treatments. In addition, the constructed animal model is more ideal and more conform to clinic pathological and physiological changes of the type of disease.