The as-cast amorphous Ti48Zr27Cu6Nb5Be14 composites, comprising in situ formed β-Ti ductile crystalline precipitates, were prepared by water cooled copper mold suction casting. Then, the semi-solid composites were obtained after the as-cast composites were treated by semi-solid isothermal treatment. The microstructure evolution and kinetics of the composites were examined. Results show that the microstructures of both the as-cast and semi-solid composites comprise of β-Ti crystal phases and amorphous matrix phases. Before and after treatment, the crystals evolve from fine granular or fine dendritic crystals to coarse crystals. As the treatment temperature increasing or the time prolonging, the average crystal size gradually increases and the surface morphology of the crystals gradually becomes regular. By studying the microstructural evolution and dynamics during the isothermal treatment process, it is found that the final morphology of β-Ti crystals is influenced by the isothermal treatment temperature and time (t), and the β-Ti evolution rate increases with an increase in treatment temperature. In addition, a linear relationship was observed between the size of cubic β-Ti crystals (D³ ) and t; the growth kinetics factor K is 3.8 μm³ ·s^-1. As the K value closes to 4 μm³ ·s^-1, it is inferred the morphology evolution of β-Ti crystals is a coarsening behavior controlled by the diffusion of solute elements.