This study was conducted in solar greenhouse where cucumber was cultivated in winter-spring
season．During cotyledon flattened period to the second leaf starting flattened，cucumber seedlings was treated
with supplementary light at different time．During experiment period heat preservation quilt was uncovered from
8：40-16：00 in solar greenhouse．The results showed that compared with the contrast without supplementary
light，supplementary light treatment at T（6：40-9：40），T（13：00-16：00） and T（15：00-18：00）
could significantly increase seedling stem diameter，healthy seedling index，leaf area，contents of chlorophyll，
carotene，soluble sugar，starch，etc．and seedling dry weights of underground，over ground parts and whole
plant．To sum up，the effects of supplementary light by the above 3 treatments are obviously superior than that of
T（8：40-11：40） and the contrast．These 3 treatments are in favor of cultivating healthy seedlings．The effects
of these 3 treatments are basically the same．