Abstract: Calcium content is an important indicator of milk.To accurately detect the calcium content in liquid milk, and further explore the dry ashing method in the national standard method.By conducting single factor and orthogonal experiments, the detection method was optimized using the spiked recovery rate as the indicator and validate and apply the method.The experimental results showed that：The amount of lanthanum solution added was 2.5 mL, nitric acid solution was 5 mL（1+1）, （Heating at 180 ℃ for 5 min 230 ℃ for 5 min, 300 ℃ for 5 min, 400 ℃ for 10 min, 500 ℃ for 20 min） gradually increase temperature and carbonize, ashing at 550 ℃ for 4 h was the optimal detection condition, the accuracy of the test results can be guaranteed。

Key words: flame atomic absorption, dry ashing method, milk, calcium