The setup and principle od damper cooling tube (DCT) process to prepare the semisolid slurry of A356 aluminum alloy were introduced in different pouring temperatures. The results of measured and calculated grain size and shape factor in castings microstructure show that they are directly related to the pouring temperature, the lower the pouring temperature, the smaller the grain size and shape factor, due to the formation of stray nucleus and the cooling and stir of DCT. The semisolid slurry or billet produced by DCT processis are suitable for the semisolid processing owing to the fine grain size and spherical primary particles.