The purpose of this paper is to investigate the changes in IPO pricing efficiency and IPO underpricing level following a regulatory reform (No.78 [2012] CSRC) of cancelling the 180-days lockup period in China, using data of IPOs on either Shanghai or Shenzhen stock exchanges of China from 18/5/2011 to 02/11/2012.Ever since Chinas Securities Regulatory Commission (short for CSRC) has established, it did a lot of continuous research and changes in regulatory methods of securities issuing and management.In may 11 th 2012, the C SRC decided to cancel the 180 days lockup period in "the decision of about amending management methods of securities issuing and underwriting"approved in [The 78st bill] , which will be promising to improve the liquidity of newly issued securities.As proved by domestic academics in their investigation of lockup period, the demand curve for Chinese IPO shares is downward to the right and lockup limits the volume of available trading securities.Combined by this two factors,we can come to the conclusion that there will be higher trading price of newly issued securities and thus the lockup period will not improve the IPO pricing efficiency.Since the newly issued policy cancel the 180 days lockup period, we grasp the opportunity to further investigate in the effect of caneelling of lockup period.The statistics and analyse show us that the percentage of IPO P/E deviating from the P/E of belonged industry (nearly a month) increased.Thus, we can deduce that there are more bubbles embedded in the offering price and that our financial market does not obtain a better IPO pricing efficiency.Moreover, we calculate the abnormal return and cumulated abnormal return of the 82IPOs dating from 18/05/2012 to 02/11/2012, the result of statistics suggest that the CAR trend it upward which indicate that the prices of those 82 stocks perform well during post-IPO 90 days.