本文分析了降解ＤＮＡ作ＰＣＲ分型易失败的原因，提出了因小片断ＤＮＡ过多，阻碍引物与膜机的复性及阻断引物延伸的新现点。将降解的ＤＮＡ电泳，切除小片断ＤＮＡ，电洗脱回收较大片断ＤＮＡ，成功地对降解ＤＮＡ进行了ＰＣＲ分型．本方法简便、快速、有效。 In this paper, the reasons for the failure of PCR to degrade DNA were analyzed. Some new points were suggested that the DNA fragment was too small due to the small fragment, which hindered the refolding of primer and membrane and blocked the extension of primer. The degraded DNA was electrophoresed, a small fragment of DNA was excised, and a larger fragment of DNA was eluted by electroelution, and the degraded DNA was successfully typed by PCR. The method is simple, fast and effective.