History is often marked by the materials and technology that reflect human capability and understanding. The increasing needs on bio-degradable and eco-friendly nature for consumer goods, the usage of bio-based materials is on demand. Flax has attracted attention since Stone Age as one of a few plants from which highly valued products are made. Fibres from flax plants are cost-effective, bio-degradable and exhibited good mechanical properties. This review focuses on the preparation, properties and prospects of flax fibres and its composites. The plant growth, harvesting, fibre structure, properties, effect of chemical treatments, influence of various factors such as fibre length, diameter, fibre location, fibre orientation on properties of composites, and processing-structure-property relationships have been reviewed. Then the effect of fibre configuration, manufacturing processes, fibre quantity, matrix selection, ecological effects, mechanical properties, life cycle assessment, failure studies and fibre/matrix interface parameters on the characteristics of flax fibre composites have also been analyzed. Many open issues and ideas for further improvement are also analyzed, and more emphases are given for the development of environment-friendly bio-inspired material. Focusing on the summary of the review and the effects of the flax fibres on the finished products are also presented in this review.