Abstract: With LED light source，four light quality treatments（white light，red light，blue light，a combination of red and blue light）were carried out to investigate their effects on growth， photosynthetic characteristics，female number and yield in cucumber plants. The results showed that compared to white light，red light significantly inhibited cucumber growth，declined photosynthetic characteristics，decreased CO2 assimilation rate（Pn），electron transport rate in PSII（ETRII）and effective PSII quantum yield（ΦII），whereas increased quantum yield of light-induced（ΦNPQ） and non-light-induced（ΦNO）non-photochemical fluorescence quenching. Meanwhile，red light delayed flowering time of first female flower，decreased cucumber numbers and total yield in initial stage. A combination of red and blue light significantly decreased root shoot ratio，however increased total leaf area，female flower numbers in the first 20 nodes and total yield in initial stage. Blue light decreased plant height and leaf numbers and accelerated flowering time of first female flower. In conclusion，a combination of red and blue light enhanced total leaf area，increased female flowers and initial yield in cucumber plants.

Key words: cucumber, light quality, growth, photosynthetic characteristic, flowering time, yield