Abstract : The study focused on the content changes of polyphenol and chlorophyll, and antioxidant activities of Centella asiatica grown in Khanh Hoa province, Vietnam according to the growth times of 30 to 120 days. Extracts from Centella asiatica were collected by using ultrasonic-assisted extraction and various antioxidant activities were evaluated such as total antioxidant activity, reducing power activity, and DPPH free radical scavenging activity. Results showed that the highest chlorophyll content of 5.104 ± 0.041 mg chlorophyll equivalent/g DW at the 45th growth day of centella. Polyphenol content and reducing power activity got the highest value at 75th growth day of Centella, corresponding to 14.156 ± 0.026 mg gallic acid equivalent/g DW and 22.891 ± 0.040 mg FeSO4 equivalent/g DW, respectively. Centella asiatica possessed the highest total antioxidant activity and DPPH free radical scavenging activity at the 60th growth day, corresponding to 6.059 ± 0.022 mg ascorbic acid equivalent/g DW and 79.49 (%), respectively. The correlation between polyphenol content and reducing power activity was higher than other correlations. Centella asiatica is useful in the production of antioxidant medicine plants applicable to functional food and pharmaceutical antioxidants.