Abstract: 1. The formation and accumulation of chlorophyll in cotyledons of etiolated soybean seedlings was found to be promoted by ascorbic acid treatment. 2. The increments of chlorophyll contents in soybean cotyledons by ascorbic acid treatment were different at different temperatures, and there was an optimum at 30 ℃. 3. The absolute contents of chlorophyll in cotyledons were increased with the length of etiolated soybean seedlings. 4. The amounts of required ascorbic acid at different ages were different. Young and old seedlings were more sensitive than middle aged ones. 5. If soybean seeds were soaked in the solution of ascorbic acid before germination, there was more chlorophyll being formed and accumulated in etiolated cotyledons. 6. If the seeds were treated by ascorbic acid, the increase of chlorophyll a was greater than that of chlorophyll b, but when the seedlings were treated, the increase of chlorophyll b was greater than that of chlorophyll a. 7. During the illumination of etiolated soybean seedlings, chlorophyll a appeared first.