Abstract: TiB₂/7050 aluminum matrix composites have important application prospects in aeroengine and other fields. The room-temperature high cycle fatigue performance of in-situ 7050 aluminum matrix composites with 4wt.% TiB₂ particle at T6 state was studied in this work, and the fatigue fracture mechanism of the composites was analyzed by SEM. The results show that when the stress ratio R is −1 and the specified life is 3×10⁷ cycles, the fatigue strength of TiB₂/7050 composite is 211.92 MPa, which is higher than that of 7050 Al alloy. The macroscopic morphology of the fatigue fracture includes fatigue propagation source area, fatigue area and final rupture regions. The fatigue crack initiation sources are mainly in the areas of inclusions, large-size TiB₂ particles and microscopic pores close to the sample surface. When the fatigue crack expansion encounters the TiB₂ particle band, the width of the fatigue striation significantly reduces, i.e. the TiB₂ particles improve the fatigue crack expansion resistance of the composite, enabling the composite to have a high fatigue life.