The superior properties of beta titanium alloys make them being more and more widely used in structural applications like aerospace industry. There is continuing need for more investigation on the processing-microstructure-properties relationship of beta alloys, with an emphasis on fracture toughness. This project studies the mechanism of microstructural features influences on mechanical properties, with the aim to optimise fracture toughness while maintaining the yield strength and ductility. The obtained knowledge is also used to develop a model incorporating microstructure to predict the plane strain fracture toughness without complex and expensive mechanical testing.