The main pattern and causes of the alteration in blood biochemistry indices in coccidia-infected broilers were studied with principal component analysis. The result showed that infection with Eimeria spp. mainly affected levels of serum protein and lipids. Variability of serum indices was related to the parasitic site and pathogenicity of strains (or lines) with which the chickens were infected.The strain which had the most profound effect on the serum constituents was E. acervulina,E. tenella parent line came in next,while the effect of E. maxima precocious line on blood indices was least. The characteristic changes in the serum of E.tenella and E. maxima precocicus line groups was alteration in serum lipids.Infection with E. tenella and E. acervulina parent line affected lipids and proteints to the same extent.