Abstract: In order to explore the method that fast distinguishes the aroma of orange juice and mandarin juice and monitor the quality during process, the electronic nose was applied to discriminate the overall aroma of orange juice and mandarin juice. The effect of aroma on different process during sour orange juice processing and discrimination of different processing type were also studied. The acquired data were analyzed by principal component analysis (PCA) and discriminate factor analysis (DFA). The results indicated that the aroma quality of orange juice and mandarin juice from different variety present diversity. Meanwhile, the aroma had taken place significant changes after processing. The aroma of reconstituted orange juice was weaker than NFC（not from concentrated）juice. The electronic nose sensor signal of 4 kinds of reconstituted juice with different soluble solids (28%，38%，48%，63.5%) existed linear relationship. The 55% reconstituted juice was chosen as unknown sample to discriminate the concentration. The discriminate result was 57.95% with 5% RSD. The electronic nose could be used in the detection of the citrus juices from different varieties and processing type, also monitor the orange juice process.