In this paper, failure behavior of basalt specimen containing 3D-flaw with different angles is investigated under triaxial compression. The process of crack growth was observed by computerized comography (CT). Based on the experimental results, the following conclusions were obtained: Under 3D loading condition, the angle of pre-existing flaw has a dominating influence on the zone of stress concentration. When the flaw angle is parallel to the direction of vertical loading, the failure peak strength is greater than that of sample containing other flaw angle, and the final failure mode is irregular. When the pre-existing flaw angle is about 60 degree with horizontal loading direction, stress concentration is easy to form at the tip of pre-existing flaw, and lead many small radicalized cracks to propagate. Under 3D loading condition, the cracking surface generally is distorted and lead crack to propagate in irregular direction, and then form irregular space failure with mixed mode. The experimental results observed here has shown that the experimental system and method in this study is efficient and robust.