The photosynthetic adaptability of two color-leafed flowering shrubs i.e. Spiraea bunmalba ‘Goldmound’ and Spiraea bunmalba ‘Goldflame’ to weak light stress was studied, the changes of photosynthetic characteristics during weak light treatment and recovery processes were analyzed, and the changes of physiological adaptability under weak light environment were explored in order to provide reference for the scientific applications of Spiraea L. in the different light environments of city gardens. Two species Spiraea L. displayed obvious diurnal variation of photosynthesis, P_n diurnal variation presented double-peak curve when the light intensities were 60%-65% and 40%-45% of natural light, the first peak value was higher than the second one. There were obvious phenomena of "Midday Photosynthetic Depression". When the light intensity was 20%-25% of natural light, P_n diurnal variation was single-peak curve, there was no obvious "Midday Photosynthetic Depression". P_n, LCP, LSP, AQY and Rd of 2 species Spiraea L. decreased, the contents of chlorophyll and carotenoid increased and Chla/Chlb decreased with the decrease of light intensity. The leaves of 2 species Spiraea L. became thinner, the epidermal cells of two sides became smaller, the thickness of palisade tissue and spongy tissue became thinner, the intercellular space of spongy tissue became bigger, the ratio of two tissues reduced with the decrease of light intensity. Two species Spiraea L. had produced specific proteins with low molecular weight (45.0-66 kDa) under the weak light stress, they might be the induced proteins. Two species Spiraea L. had certain recovery ability after 60%-65% and 40%-45% weak light treatments, their recovery ability was weak when light intensity was 20%-25% of natural light. The thickness ratio of palisade tissue to spongy tissue, chlorophyll a/b and P_n were the important indicators in evaluating the resistance ability to weak light of 2 species Spiraea L. The value of chlorophyll a/b presented a significantly negative correlation while the thickness ratio of palisade tissue to spongy tissue and P_n presented significantly positive correlations with the resistance ability to weak light. According to the value of membership function, the resistance ability to weak light of 2 species Spiraea L. was S. bunmalba ‘Goldflame’ > S. bunmalba ‘Goldmound’.