Abstract: In order to investigate the relationship between Ca²⁺ overload and the injury of host cell of E. tenella infected chicken, the amount and the distribution of calcium, Na⁺K⁺ATPase, Ca²⁺Mg²⁺ATPase, the total ATPase, PLA2, free fatty acid in caecum tissue as well as free Ca²⁺ in caecum epithelium were examined. The results showed that in the process of E. tenella infection, the content of calcium and Ca²⁺ increased obviously(P<0.01) with the severity of the disease. The activity of Na⁺K⁺ATPase，Ca²⁺Mg²⁺ATPase，the total ATPase in caecum tissue all decreased with the developing of the disease. In the serious phase of disease, the activity of these ATPases were significantly lower than that of the uninfected control group (P<0.01). Obviously elevated activity of PLA2 and the content of free fatty acid demonstrated that overloaded calcium played an important part in the injury mechanism. Nifedipine could block the Ca²⁺ internalization and decrease the Ca²⁺ level in host cell, therefore could ease the injury and provide certain protection, but only effective in the initial phase of disease while the damage was slight and its function declined later.