The invention relates to a vein image quality detecting method for characteristic extraction, comprising the four treatment stages: pre-treatment of a finger vein image, division of a finger vein image region, first-grade quality judgment of the finger vein image and second-stage quality judgment of the finger vein image. The treatment stage of the finger vein image comprises the following steps of: firstly, locating a target position by using a fixed threshold method and cutting a target region; and then carrying out size normalization. The division of the finger vein image region comprises the step of dividing the finger vein image into a plurality of regions along the way of the finger vein so as to be beneficial to extracting subsequent significance characteristics. The first-stage quality judgment stage of the finger vein image comprises the steps of: firstly, extracting average gradient characteristics of regional rows of the finger vein image; secondly, judging whether the quality of the finger vein image is qualified, and entering the second-stage quality judgment flow of the finger vein image when the finger vein image is unqualified in the first-stage judgment. The second-stage quality judgment stage of the finger vein image comprises the steps of: firstly, extracting texture detail indexes of the finger vein image; and secondly, judging whether the quality of the finger vein image is qualified, and reminding a user of replacing other fingers to register when the finger vein image is unqualified. The vein image quality detecting method for characteristic extraction, disclosed by the invention, can be used for effectively detecting the quality of the finger vein image, automatically selecting available fingers in the user registration and restraining adverse influence of low-quality vein image on the performance of a finger vein identification system.