Abstract: 【Objective】 This study aimed to performed quantitative and semi-qualitative analyses of proteins in pineapple wine， investigate the impact of gradient tannin addition post-fermentation on protein stability， and evaluate its effects on the physiochemical properties， aroma substances， and sensory quality， providing references for quality improvement and process optimization of pineapple wine.【Method】 Five treatment groups were set： control group （CK）， gradient tannin addition groups （T50， T100， T150， with tannin additions of 50， 100， and 150 mg/L， respectively）， and a heat treatment combined with tannin addition group （H50， adding 50 mg/L tannin after 80 ℃ water bath for 30 min）. SDS-PAGE electrophoresis and Bradford method were used to analyze protein composition and content in pineapple wine under different treatment groups. Linear regression and correlation analyses were conducted to explore relationship between tannin addition amount， protein content， and pineapple wine sample quality indexes. Aroma substance composition was analyzed using headspace solid-phase microextraction-gas chromatography-mass spectrometry （HS-SPME-GC-MS） with partial least squares-discriminant analysis （PLS-DA）. Furthermore， partial least squares regression （PLSR） was employed to analyze the relationship between aroma substances and sensory attributes.【Result】 The protein content in pineapple wine was 0.29 g/L， with molecular weights of approximately 21.0 and 14.4 kD. Tannin addition amount showed a linear correlation with protein removal （R²=0.9553） and was significantly positively correlated with the clarity， brightness， and astringency of pineapple wine samples （P<0.05， the same below）. Different tannin addition amounts （T50-T150 groups） had limited effects on the physiochemical properties of pineapple wine， but all significantly increased the total amount of aroma compounds， especially the contents of higher alcohols， esters， and volatile phenols. Isoamyl alcohol， phenethyl alcohol， isobutanol， ethyl lactate， and ethyl acetate were identified as key aroma substances significantly affected by tannins. Among them， the ethyl acetate content in tannin-added groups significantly increased by 15.7%-22.5% compared to the CK group， while the isobutanol content significantly decreased by 10.3%-12.6%. For sensory qualities， the T50 and T150 groups showed more prominent spice and dried fruit aromas， the T100 group showed more prominent peach and pineapple aromas， and the CK group was mainly featured by muskmelon and herbal aromas. In addition， the H50 group effectively removed unstable proteins from the pineapple wine； however， octanal with an undesirable chemical odor was detected in the samples. Moreover， the acetic acid content was excessively high， around 64 times that of the CK group， which would add a vinegar smell to the wine.【Conclusion】 Pre-fermentation tannin addition can effectively improve protein stability of pineapple wine， optimize its aroma substance composition， and enhance sensory quality， with the best comprehensive performance at a tannin addition amount of 150 mg/L. Although heat treatment with tannin addition can well enhance protein stability， it may also lead to the loss of important aroma substances and acetic acid accumulation. Therefore， the process of pre-fermentation heat treatment of pineapple juice requires more detailed evaluation and optimization.