The principal problem of the development of facility agriculture in northern China is the frequent low irradiation weather in autumn and winter.In greenhouses,most environmental factors required for crop can be artificially regulated except light.Tomato is one of the main facilities crops in Shandong province.It is important to study the effect of light on facility tomato for agricultural production in Shandong.In order to study the enzyme activity of tomato leaf under different shading days,taking the infinite-growth-typed tomatoes ‘Power Corolla’ as experimental material, five shading treatments of tomatoes were set in greenhouse during the flowering and fruiting period, they were T1 (3-day shading), T2 (6-day shading), T3 (9-day shading), T4 (12-day shading) and T5 (15-day shading), respectively, and the growth of tomatoes under natural light in solar greenhouse was used as the control check .The results showed that low irradiation would increased the enzyme activity of tomato leaves and reduced the leaf weight.As the number of shading days has increased,the recovery capability of enzyme activity and leaf weight on tomato leaves would reduced.Long shading time (above 12 days) would cause irreversible damage to the photosynthetic system of leaf and making the enzyme activity unrecoverable.