【Objective】 To study the injury to immune organs of piglets from three kinds of PRRS vaccine（MLV, TJM 92 and JXA-1R vaccines）.【Method】Fifty new-born healthy piglets were devided into four groups：non-immunized control group(CK group), MLV vaccine group(A group), TJM 92 vaccine group (B group), JXA-1R vaccine group (C group). Every piglit in the experimental group were vaccinated. Then paraffin sections were prepared after pathological anatomy. Changes in percentages of esterase-positive T cells and plasma cells (effector B cells) of different immune organs were summarized by using optimized esterase (α-NAE) and methyl green-pyronin (MG-P) staining. 【Result】There were significant or highly significant differences in the percentages of esterase-positive T cells and plasma cells of immune organs between each immunized group and CK group. 【Conclusion】Three kinds of vaccine all have injuries to immune organs of piglets. Injury from JXA-1R vaccine is the strongest, followed by TJM92 vaccine and then MLV vaccine.