Al-1.0%Si alloy rods containing unidirectional microstructures were fabricated by continuous unidirectional solidification (CUS) process. The crystal growth orientation evolution of Al-1.0%Si alloy in CUS process was studied. The microstructure was observed and the orientation results examined by electron back scattering diffraction(EBSD) indicate that at the beginning of CUS from this preferred orientation. It is found that as directional solidification continues, the crystals with high growth speed remain and When the solidification parameters remain stable, the crystal growth orientation also obtains in steady state. Once the technological parameters fluctuate, the stray crystals deviating from the preferred orientation appear. After the process of competition growth the crystals regain strong preferred orientation. The orientation distribution function(ODF) results also testify the above conclusions.