In the construction projects invested by Chinese government, the owners are often affected by their personal preference such as taste standpoint or individual achievement when they are making decisions. At the same time, the designer caters to the owner's pleasure for the sake of benefit. As a result, there are too many"face projects" , "achievement projects" in China`s cities. The principal-agent model is used in this article to analyze the change of owners`investment benefit and designers' effort under law-abiding and speculation conditions. It is concluded that the speculation activities can be efficiently reduced by strengthening supervision power and increasing the owners' and the designers' political risk cost.