Two field experiments were conducted for trapping efficiency of two kinds of sex pheromone lure for the diamond back moth, Plutella xylostella (L.) in Raoyang County, Hebei Province and Rudong County, Jiangsu Province in May and June, 2006. Water trays with rubber plug were baited with different sex pheromone blends A and B. The results showed that the mean number of the diamond back moths trapped by lure B was 2.12 and 3.94 fold of that by lure A in Raoyang and Rudong locations, respectively. The difference was significantly (P<0.01). Similarly, the maximum trapped numbers by lure B in one night were significantly higher than that lure A (P<0.01) at both two locations.