Background: Chaenomeles speciosa, also known as “Mugua” in Chinese, is a medicinal and edible plant with a long history of use. The optimal harvest time for Chaenomeles fruits is not clear. Objectives: This study aimed to determine the appropriate harvest time for different uses of Chaenomeles fruits. Materials and Methods: Agronomic characteristics, chemicals, and antioxidant activity of fruits were detected at several developmental stages (15, 30, 45, 60, 75, 90, 105, 120, 135, and 150 days after full bloom [DAFB]). Results: Based on agronomic characteristics (length, diameter, fresh weight, and dry weight), the whole development period was divided into rapid growth and slow growth stages. Physicochemical characteristics (flavonoids, triterpenes, and polyphenols) and pentacyclic triterpenoids (oleanolic acid and ursolic acid) were used to distinguish medicinal usage. Organic acid content (shikimic acid, quinic acid, malic acid, protocatechuic acid, and chlorogenic acid) was the major consideration for edible fruits. Principal component analysis and partial least squares-discriminant analysis were performed based on the whole indexes, and all developmental stages were divided into six clusters. Quinic acid, malic acid, shikimic acid, and oleanolic acid showed a positive relationship with antioxidant activity. Conclusion: The results showed that the 105–120 DAFB fruits were most suitable for use as Chinese medicine and the 120–150 DAFB fruits might be most suitable for use as edible flavored fruit.