Chlorophyll is a very important pigment involved in photosynthesis,its biosynthesis plays a key role in conversion of light energy into chemical energy and stored in organic through photosynthesis.In higher plants many genes responsible for the Chl biosynthesis pathway were identified and the enzymatic steps of the pathway were characterized.Here we report the characterization of a LACS gene BnCHS from Brassica napus.The cloned gene BnCHS can complement a LACS-deficient yeast strain YB525.It is mainly expressed in leaves of Brassica napus.When transiently expressed in tobacco and Brassica napus cotyledons,the BnCHS-GFP is localized in chloroplast,and increase the chlorophyll b both in tobacco leaves and rapeseed cotyledons.Overexpression of BnCHS in Brassica napus resulted in increasing the contents of galactodlipid,the chlorophyll B and the weight of the biomass.Taken together,our results suggest that BnCHS is involved in chlorophyll B biosynthesis in Brassica napus and overexpression of BnCHS increased the biomass of Brassica napus and the BnCHS have a potential role in improving the seeds production.