The work aims to reduce the negative discoloring and whitening rate of anode in aluminum alloy mobile phone shell. CE matrix of factor was prepared and PEMEA analysis was executed based on DMAIC system in six sigma management and processing technology of some certain mobile phone shell according to causal graph between rework flowchart and key factor. Then, 5 key quality influence factors were determined, including drug concentration, ultrasonic frequency, tank liquor temperature and soaking time R400 support pickling tank and hot air cleanliness in drying tank. Equally study method was adopted to solve problems like air filter element in drying tank not being regularly replaced or not replaced over one month, low cleanliness of blown hot air and discoloring of products and the replacement standard of air filter was prepared. Through two-level four factorial experiment design, the negative discoloring and whitening rate increased as the drug concentration went up, but decreased along with increase of tank liquor temperature, soaking time and ultrasonic frequency increase. Tank liquor temperature and drug concentration were interacted. Then, the control strategy of the drug concentration, ultrasonic frequency, tank liquor temperature and soaking time of the R400 support pickling tank was designed. The range of each parameter of pickling tank: drug concentration from 35 g/L to 40 g/L, ultrasonic frequency 3.5 A, tank liquor temperature from 25 ℃ to 27 ℃ and soaking time from 3.5 min to 4 min. The rules on replacement time of the drying tank: replacement every 15 days and inspection for cleanliness of air filter element every 5 days. The negative discoloring and whitening rate drops to 1.14% from 6.63% before the improvement and reaches the target of 2%. Cost decreased by more than 900,000 Yuan for 4 weeks.