This paper studies the effects of auction mechanisms on the average price of auction results of Shanghai car license plate from 2004 to 2018. We construct two linear regression models and find that an iterated multi-unit auction has a lower efficiency than a seal-bid discriminatory multi-unit auction. We also find that the pre-set price-ceiling is positively correlated with the average winning price. These results suggest that the government can potentially manipulate auction results through the design of the auction mechanism, and through the setting of warning price as a price ceiling.