OBJECTIVE：To study the effects of the deregulation of drug price control on drug price ，and to provide reference for policy formulation. METHODS ：The quarterly price data of 46 875 chemical and biological products （measured by fixed Laspeyres index ）were collected from 788 sample hospitals from the database of National Medical Economic Information Network during Jan. 2012 to Jun. 2017. Based on the interrupted time series model ，changes in the prices of overall situation of chemicals and biological products ，as well as the sub-group ，ie. low-cost drugs ，original and imitated drugs were analyzed after the government’s policies of canceling the price limit control and strengthening the price monitoring （including Notice on Printing and Distributing the Opinions on the Supply and Guarantee of Commonly Used Low-cost Drugs in 2014，Notice on Printing and Distributing the Opinions on Promoting the Reform of Drug Prices in 2015，etc.），returning to market competition ；the effects of canceling the price limit control on drug price were put forward. RESULTS & CONCLUSIONS ：After government deregulation for maximum retail price limit of commonly used low-priced drugs ，the price of low-priced drugs increased substantially （β3＝1.11×10－2， P＝0.008）. After the total abolition of drug price control ，there was no significant change in the overall chemical and biological products（β3＝－1.85×10－3，P＝0.175）and sub-group （low-cost drugs ：β3＝1.10×10－3，P＝0.066；original drugs ：β3＝－7.20×10－4， P＝0.549；generic drugs ：β3＝6.78×10－4，P＝0.784）drug prices. Within two years after government deregulation policy in 2015， drug prices and the drug market had remained stable. It can be seen that it is feasible for canceling the government ’s pricing and opening the price control in the mature market so as to make the price formulation return to the market ，combined with the government strengthening the price monitoring.