Abstract: In March 2021, 1-year seedling of Symphyotrichum novi-belgii‘Lilac Blue’, S. novi-belgii‘Winston S. Churchill’, S. novi-belgii‘Sasha’, S. novi-belgii‘Eva’and S. novi-belgii‘Nicole’were transplanted in pot and moved to greenhouse in Hangzhou, Zhejiang province. In July of the same year, 3 individuals of each cultivars were selected to determine the diurnal variation of photosynthesis, light intensity-photosynthetic rate curve and chlorophyll content. The results showed that the diurnal variation of net photosynthetic rate (Pn) of 5 cultivars displayed a bimodal curve model, and had the phenomenon of “Lunch break” of photosynthesis, the average net photosynthetic rate was ordered by ‘Lilac Blue’ > ‘Winston S. Churchill’ >‘Sasha’ > ‘Eva’> ‘Nicole’, and the peak time of net photosynthetic rate was different among plants. Correlation analysis showed that stomatal conductance (Gs) had extremely significant relation with Pn, was the main factor affecting the diurnal variation of Pn. Analysis on the parameters obtained from the nonlinear fitting of the light response curve and the chlorophyll content, it showed that 5 cultivars were shade-enduring. TOPSIS was used to analyze LCP, Rd , AQY and Ca/Cb of the tested cultivars. The order of shade enduring of the five cultivars was as follows: ‘Eva’ >‘Nicole’ > ‘Winston S. Churchill’> ‘Sasha’ > ‘Lilac Blue’.