In order to investigate biochemical activities of harvested tobacco leaves, photosynthetic rate, soluble protein contents, and peroxidale activities were analysed during different maturing period. Physiological activities of harvested leaves during maturing period were higher in topped than those of non-topped plants. Chlorophyll content and photosynthetic rate in both topped and non-topped plants decreased at 4 days and 3 days before harvest, respectively. The chloroplast numbers in topped and non-topped plants decreased at 3 days and 5 days before harvest, respectively. Changes of soluble protein and total RNA contents showed similar patterns during maturing period. Soluble protein contents were slightly decreased from 5 days before harvest in topped plants, but decreased drastically from 3 days before harvest in non-topped plants. Not much changes were found in total RNA contents in topped plants until 2 days before harvest, and it was largely decreased after 5 days before harvest in non-topped plants. The peroxidase activities drastically decreased in topped plants and increased in non-topped plants after 3 days before harvest during maturing period. The largest change of biochemical activities in tobacco leaves during maturing periods were observed at 3 days before harvest. Key words : maturing period topping, soluble protein, photosynthesis, peroxidase activity. Nicotiana tabacum