The fluidity of in-situ synthesized (TiB+La₂O₃)/Ti composite is investigated by using a vacuum fluidity test. The cast ingots were prepared in consumable vacuum arc-melting furnace. Spiral fluidity test was carried out in vacuum consumable electrode condensing furnace. The microstructures and reinforcements are examined by means of optical microscopy. The big β grain and Laminar α are observed on root of spiral fluidity specimen. The big β grain and Laminar α are smallest on top of spiral fluidity specimen. TiB reinforcements are evenly distributed in the matrix. The addition of reinforcements would enlarge the crystallization and solidification region of the TMCs. The termination mechanism of the melt flow is attributed to the continuous growth of equiaxed grains. Specifically, the decrease in the diameter of pores in between grains would reach a critical value that finally stops the flowing, due to a sufficient friction between the melt and equiaxed grains.