Abstract: 1. By means of paraffin sectioning and Tuan's cell separation technique, leaf cells of normal and weak seedlings of winter wheat were studied. These seedlings belong to 3 varieties of winter wheat, they are, North China 187, Agricultural University 15 and 90. 2. The mesophyll cells of winter wheat seedlings are of many types, many of them are in the shape of comb, chain, etc., however the young leaves have more single cells than those of the flag leaves as described by Tuan. 3. The mesophyll cells of winter wheat are arranged inside the leaf with their wide axes parallel to the longitudinal axis of the leaf. The high axes of mesophyll cells are often at right angles to the epidermis of the leaf. 4. The average size of the mesophyll cells and average size of chloroplasts in the mesophyll cells of normal seedlings are larger than those of the weak seedlings. 5. The percentages of large chloroplasts (the longest diameter of the chloroplasts= 6–8μ) are more than 51% (51%–77.5%) in the normal seedlings, they are less than 14% (2.5%–1.4%) in the weak seedlings. 6. The cell-shape and cell-arrangement of the mesophyll cells of wheat, and the size differences of the mesophyll cells and chloroplasts between normal and weak seedlings have been discussed. 7. It is advantageous to use the technique of cell separation and paraffin sectioning together in the studies of leaf cells.