An improved silver ammonia staining method for DNA on polyacrylamide gels is described. In this method, staining of DNA using silver ammonia complex allows high sensitivity, low cost, low toxicity, and simple protocol without requiring fixation and sensitization steps. The protocol takes less than 40 min to complete, with a detection limit of 1.5 pg of single DNA band on polyacrylamide gels, approximately 30-fold higher than that of original silver ammonia staining method. Furthermore, this novel technique not only exhibits high sensitivity for large DNA fragment, but also shows a better trend to detect low-base-pair DNA compared with other silver staining methods.