It is common limiting technological issue and research focus of whole world brewing industry to improve flavor stability, including bitterness stability, with an aim to keep refreshing character of beer as long as possible to attract consumers in the shelf life of beer. Beer bitterness is mainly endowed by soft resin (i.e. α/β-acids), hard resin as well as their derivatives. With the help of modern purification technologies, nuclear magnetic resonance spectroscopy and high resolution HPLC MS, the overseas researchers have took some breakthroughs in identifying the compounds of α/β-acids derivatives and complicated hard resin. In this paper, the highlights of the newly identified bitter compounds originated from hop β-acid and hard resin were reviewed in detail, especially the relevant proposed reaction mechanisms, thresholds and elution of them during brewing and storage were introduced, in order to let beer brewing peers in China to enlarge knowledge of the complicated beer bitter quality in depth.