Abstract: The present study focuses on the relationship between microstructure and toughness property in the coarse grain heat affected zone (CGHAZ) of Q890 high-performance steel. The result show that, with the heat input increasing microstructure changes from martensite to martensite and bainitic ferrite and then to bainitic ferrite and granular bainite. The Charpy impact test results show that impact energy as high as 83 J attained in the CGHAZ with 19.7 kJ/cm, which related to the contribution of prephase bainitic ferrite segment martensite and leading to maximum density of high angle boundaries, which can improve toughness. When the heat input is 34.1 and 44 kJ/cm, the impact energy reasons for the decline is due to catenulate distribution of embrittlement M-A constituents and local stress concentration, resulting in rapid crack initiation and propagation via the massive martensite–austenite (M-A) constituent.