Korean ginseng has been used for thousands of years as an important medicinal plant. Lime-Bordeaux mixture (LBM) was made with copper sulfate and quicklime, which was sprayed instead of pesticides in ginseng field. Net photosynthesis ($P_N$) was compared between Treatment and Non-treatment of LBM in 3 Year Old Ginseng. $P_N$ in control plot recorded $2.94{mu}mol;(CO_2);m^{-2}s^{-1}$ at the first day of experiment, which was similar until the last day of experiment. However, The $P_N$ in LBM recorded $2.23{mu}mol;(CO_2);m^{-2}s^{-1}$, which was lower than that in control plot. As time goes by, The $P_N$ in LBM was gradually increased up to $3.21{mu}mol;(CO_2);m^{-2}s^{-1}$ and finally, it was similar with that in control plot at 7th day as a $3.20{mu}mol;(CO_2);m^{-2}s^{-1})$.