Linolenic acid has great effects on the structure and function of chloroplast. The function of Ce3+ on the improvement of chloro-plast photoreduction activity and oxygen evolution damaged by linolenic acid in spinach by in vitro investigation was studied. Results showed that adding Ce3+ to the linolenic acid treated chloroplast could greatly decrease the reduction linolenic acid exerted on the whole chain electron transport rate and the photoreduction activity of photosystem Ⅱ (PSⅡ) and photosystem Ⅰ (PSⅠ) as well as the oxygen evolution rate of chloroplast. It indicated that Ce3+ had the ability to relieve the inhibition of the photochemical reaction of chloroplast caused by lino-lenic acid to some extent.