The texture of rotary-veneer can interference in defects detection, this paper presented a modified semi-fuzzy clustering (SFC) algorithm. SFC algorithm incorporates Fisher discrimination method with fuzzy theory using fuzzy scatter matrix. By iteratively optimizing the fuzzy Fisher criterion function, the final clustering results are obtained. SFC algorithm exhibits its robustness and capability to obtain well separable clustering results. This algorithm can detect the texture and defects on rotary-veneer surface exactly.