Microstructure of high strength aluminium alloy have determinant effect on the properties, thus an effort has been made to investigation the relationship between fracture toughness and quantitative characteristics of microstructure in high strength aluminium alloy.Fracture toughness was tested for aluminium alloy specimens with various microstructure.The corresponding microstructure was observed by metallography and electron back-scattered diffraction, and quantitative characterization was conducted by further analysis of result obtained.Correlation between fracture toughness and parameters included grain size, percentage of recrystallization, substructure content and area fraction of residual phases was investigated.It was shown that percentage of recrystallization was a crucial factor for the fracture toughness, and correlations were established with proper and reasonable correction.