Since the outbreak of coronavirus disease 2019(COVID-19), the author has been involved in the treatment of COVID-19 in the first line. It is found that some patients had a long viral nucleic acid negative time, and even the course of the disease lasted more than 40 days. After a thorough investigation of the root causes, it is found the four possible causes were: Blood stasis syndrome is difficult to remove; Damp heat sticky greasy; Stubb basic diseases; weak constitution. All the patients treated with traditional Chinese medicine have ted negative, and now the typical cases were analyzed and summarized in order to provide reference for the traditional Chinese medicine treatment and scientific research of the patients with COVID-19 who were difficult to t negative.