A recycled polyester fiber is provided. The recycled polyester fiber is made of a raw material by melt spinning. The raw material includes 95.0 wt % to 99.99 wt % recycled polyester pellet formed from recycled bottle chip and 0.01 wt % to 5.0 wt % titanium dioxide slurry. Based on the total weight of the titanium dioxide slurry, the titanium dioxide slurry includes 20 wt % to 50 wt % bio-oil acting as carrier, 50 wt % to 80 wt % titanium dioxide powder, 0.1 wt % to 5 wt % dispersant, 0.01 wt % to 3 wt % antioxidant, and 0.001 wt % to 0.1 wt % dye.