Malus halliana Koehne flowers have been used as a Chinese traditional medicine to treat metrorrhagia. In this study, the dynamic changes in its secondary metabolites and spectrum-effect relationship of inhibition on α -glucosidase during blooming were investigated. The changes in the contents of three flavonoids (phloretin-4’- O -glycosidase, afzeloside, and 3-hydroxyphloridzin) were determined by high performance liquid chromatography (HPLC) and changes in inhibitory effect on α -glucosidase were evaluated in vitro . Then, spectrum-effect relationship was evaluated by partial least square method. The results indicated that the contents of three flavonoids and inhibition of α -glucosidase activity in vitro showed a fluctuating downward trend, thereinto, the maximum contents of phloretin-4’-O-glycosidase, afzeloside, and 3-hydroxyphloridzin reached 157.43±0.36, 17.27±0.06 and 22.67±0.35 (mg/g), respectively. In spectrum-effect relationship assay, matched 40 mutual peaks, thereinto, P 2 , P 5 , P 6 -P 12 , P 14 (3-hydroxyphloridzin), P 16 -P 19 , P 20 (phloretin-4’- O -glycosidase), P 24 , P 26 , P 29 , P 31 , P 33 , P 34 , P 36 , P 39 and P 40 were positively correlated to inhibitory effect on α -glucosidase in vitro . P 1 , P 3 , P 4 , P 13 , P 15 , P 21 -P 23 , P 27 , P 28 , P 30 (afzeloside), P 32 , P 35 , P 37 and P 38 were negatively related to inhibitory effect on α -glucosidase in vitro .