Abstract: In the past 20 years, with the development of wind power technology, nearly 50000 tons of wind turbine blades have reached retirement age every year, and this number has increased year by year. As a composite material with high difficulty in recycling, waste wind turbine blades have become an urgent problem to be solved in terms of how to reasonably and effectively reuse resources. Among many methods, pyrolysis is considered to be one of the most promising technologies for recycling waste wind turbine blades due to its wide range of applications and high recycling efficiency. However, few people pay attention to the effect of the length of waste wind turbine blade raw materials on pyrolysis products and recycled fibers. In order to explore this influencing factor, isothermal pyrolysis experiments were carried out on waste wind turbine blades of different lengths in a tubular furnace. The pyrolysis products were oxidized in a muffle furnace to obtain pure fibers. The experimental results show that the solid yield is the highest among the three-phase products, about 68.28%–85.86%; and the gas yield is the lowest, about 1%. Pyrolysis gas is mainly composed of CO₂, CO and C1–C3 alkanes, among which the CH₄ content reaches 39.66%, and the calorific value of pyrolysis gas is about 26.16–34.11 MJ/Nm³. Pyrolysis oil is mainly composed of phenolic compounds, containing a large amount of high-value chemical raw materials such as bisphenol A, phenol, etc., and the content of compounds with carbon atoms between 6–19 reaches more than 63%. In addition, the increase in the length of the wind turbine blade can effectively improve the tensile strength of the recycled fiber. When the length of the waste wind turbine blade increases from 5 cm to 25 cm, the strength of the fiber increases from 383.9 MPa to 659.73 MPa.