Two experiments were designed at Experimental Station belonging Can Tho University in a completely random design with 6 treatments in order Hydro-cortisol to be injected 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 mg/kg body weight of Noi chickens after laying a former egg 18.5 and 19.5 hours. These experiments had 4 replicates and each experimental unit concluding 2 hens. All of hens were raised in cages, prevented by vaccines, and fed with a similar diet. The results showed that the highest offspring male ratio was 72 percent and 67.4 percent when injecting 2.5 mglkg body weight after laying a former egg 18.5 and 19.5 hours, respectively.