The effects of D- and L-phenylalanine on the Cu（Ⅱ） catalyzed oscillating chemical reaction in an alkaline medium were investigated in this paper.The results showed that the changes of amplitude（ΔA） after adding D- and L-phenylalanine were different.The changes of the amplitude were linearly proportional to the negative logarithm concentration of D-phenylalanine in the range of 1.80×10-9-1.40×10-4 mol?L-1（r=0.996 3） with detection limit（LOD） of 2.69×10-11 mol?L-1,and for L-phenylalanine in the range of 1.80×10-6-1.80×10-4 mol?L-1（r=0.995 8） with detection limit of 2.61×10-7 mol?L-1.The proposed method was successfully used for the determination of L-phenylalanine in beverage and simulating water sample.The possible reaction mechanism was also discussed.