Firstly, biaxial strength theories of fiber reinforced composite materials are briefly reviewed. The failure criteria proposed to predict composite failure can be divided into two main groups according whether to distinguishing failure modes or not. Merits and defects of different failure criteria are discussed and analyzed. Secondly, the development of biaxial testing equipments for the composites is summarized in a nutshell. Different types of specimen for biaxial loading with their characteristic problems are shown adequately. Finally, a concise assessment of biaxial strength of fiber reinforced composite materials is provided, and the future development trend is also predicted.