Abstract: The experiment was conducted to investigate the effects of dietary magnesium asparatate(MgAsp) supplementation level and different administration time length on brisket quality of broiler chickens. In Experiment 1, two hundred and fifty six male AA broiler chicks were allocated to four treatments, each treatment with eight replicates of 8 chickens. The birds were fed with the basal diet alone or supplemented with 0.3%,0.6%,0.9% MgAsp. In experiment 2, the birds were fed with the basal diet supplemented with 0.9% MgAsp from the sixth week, fifth week and fourth week，respectively, and the basal diet without Mg supplementation served as the control. In Experiment 1, pH value of brisket increased quadratically as dietary supplemental MgAsp increased （P<0.01）. TBARS value of brisket decreased linearly as MgAsp supplementation increased （P<0.01）. Dietary MgAsp supplementation significantly increased LDH activity of （P<0.05）. L value of brisket increased （P<0.05）and b value of brisket decreased as dietary MgAsp supplementation increased； In experiment 2, with the longer administration of MgAsp，except of TBARS of brisket，the quality of meat did not improve further. Dietary MgAsp supplementation can improve quality of meat, and the short time of MgAsp administration(1 week) is effective. 

Key words: magnesium asparatate; meat quality; broiler chickens