Abstract: As the injury induced by S02 appears progressively, the cells contracted and became deformed, the protoplasm and the chloroplasts turned yellow-brown or collapsed while no effects were seen in the vascular bundles generally. Howewr, as the injury induced by HF appears progressively, the cells were not deformed immediately, the protoplasm became red-brown, the mesophyll cells adjacent to stomata or vascular bundles became red-brown too, there were no effects on chloroplasts, which did not collapse until the tissue necrosis appeared, the cells of xylem and phloem turned red-brown. The process of the injury to leaf structure induced by SO2 is discussed. It is observed that destruction of chlorophyll and the interruption of photosynthesis by SO2 took place first in the palisade tissue, whereas the contraction and disintegration of the cells first in the spongy tissue. The effect of HF to the contractive collapse of chlorophyll and mesophyll occurred after the influence on protoplasm appeared.