Abstract: Objective:To study the fat oxidation kinetics and the exercise intensity eliciting maximal fat oxidation(FATmax) in endurance trained and untrained women during progressive exercise test,and investigate the effect of long-term training on fat oxidation kinetics.Methods:12 endurance trained women and 12 untrained women performed a incremental treadmill exercise test,and the index of gas metabolism was measured.The gas metabolism date in the last 30 seconds of each load was used to calculate fat oxidation rate,and use a 3rd polynomial fitting curve to determine fat oxidation kinetics curve and FATmax.Results:There are some effects on intensity of exercise and endurance training on fat oxidation rates.As exercise intensity increased,fat oxidation rate presents first increased and then decreased trend.The fat oxidation rates in 60%⁷0%O2max show relatively high level(12.20¹2.84 mg/min/kg)in trained women,and the fat oxidation rates in 50%⁶5%O2max stage has a relative high level(6.36⁶.67 mg/min/kg) in untrained women.The fat oxidation rate in same relative intensity was higher in trained women than that untrained women,and the maximum fat oxidation rate(MFO)and FATmax were higher in trained women than those in untrained women(63.95±3.16 vs 56.51±2.50%O2max,P<0.001;13.04±1.82 vs 6.71± 1.15 mg/min/kg,P<0.001).During treadmill exercise,the fat oxidation rate were more than 95% MFO for trained women in 57.14%⁶9.86%O2max and for untrained women in 48.21%⁶5.41%O2max.In addition,there are certain positive correlation between the maximal fat oxidation rate,FATmax and maximal oxygen uptake.Conclusion:1) The fat oxidation rate in same relative intensity was higher in trained women than that in untrained women,the maximal fat oxidation rate and FATmax in trained women were higher than those in untrained women.That is to say long-term endurance training can enhance the body fat mobilization and oxidation using ability.2)During running,both 60%⁷0%O2max in trained women and 50%⁶5%O2max in untrained women can induce the body fat oxidation rate more than 95% of the maximum fat oxidation rate.3) there is certain positive effect the capacity of oxygen uptake and utilization on the maximal fat oxidation rate and the exercise intensity eliciting maximal fat oxidation.