Abstract: Using‘Zhangshugang’pepper suitable for fresh and immature fruits as experimental material the changes of shape，firmness，tissue structure，main nutrients，cell wall substances，capsaicinoids and volatile components of fruit during fruit development were investigated，and the correlation analysis and principal component analysis of quality characteristics was carried out to clarify the key factors affecting the quality. The results showed that the longitudinal diameter，transverse diameter，single fruit weight，flesh thickness，fruit firmness and cuticle thickness of fruit increased gradually from the development of pepper fruits to the colour change stage. The number of pericarp cell layers did not change，and the volume of parenchyma cells increased resulting in the thickening of flesh. The contents of soluble protein showed a‘U-shaped’change with fruit development；soluble sugar and vitamin C showed an overall increasing trend；the total pectin content increased first and then decreased. The content of cellulose and hemicellulose showed a decreasing-rising-decreasing-rising trend，and the content of cellulose and hemicellulose was the lowest at 15 days after flowering. Capsaicinoids content increased rapidly in the early stage of development. A total of 158 volatile constituents were detected during pepper fruit development，dominated by terpenes，esters，heterocyclic compounds，hydrocarbons，ketones，alcohols，and aldehydes，with an increase in terpenes，esters，hydrocarbons，ketones，and aldehydes， from 10 to 25 d after flowering. Therefore，low fruit firmness，thin cuticle，moderate spiciness，low content of cellulose and total pectin content，and relatively high volatile componentsmay be the main reasons for the excellent taste of fresh and immature pepper. In addition，the results of principal component analysis showed that soluble protein content was also one of the important factors affecting the quality of ‘Zhangshugang’ pepper.

Key words: pepper, fruit development, taste, flavour substance