Abstract: We adopt the red LED at wavelength of 660 nm and the blue ones at the wavelength of 450 nm to construct the LED lamp cultivating mustard,the photon flux density used is 150 μmol·m-2·s-1.The experiment includes two groups with different filling time,and each group is divided into 4 groups in which R/B respectively 9∶1,7∶1,5∶1 and one use the natural light.After 30 days cultivation,we use Arnon＇s method with acetone and anhydrous ethanol with proportion to 2∶1 to detect the concentration of chlorophylls of mustard.The experiment results show that the chlorophyll concentration under the LED lamp with R/B ratio 7∶1 undergoes the highest one.

Key words: LED, Arnon＇s method, R/B, chlorophyll