The paper first explicate the development mechanisms of Boyang Lake's water resource exploitation and protection in their three stages,i.e.the planning mechanism,the free allocation mechanism and the regulation mechanism by government interferences.It further points out that the failure of the planning mechanism is because people look down on science,the failure of the free allocation mechanism is due to "the tragedy of public land",and the active government interferences have positive effects.Then,the paper conducts an investigation and makes a positive analysis on effects of the three mechanisms;explains that the motive force of the change from the first stage to the second stage is different from that from the second stage to the third stage,for the motive force of the former is from the power of institution reformation,whereas the motive force of the later is the result of the punishment from the nature;discovers that effects of the mechanism change from the first stage to the second stage are not good,or become even more worse because "the tragedy of public land" happens widely,and effects of the mechanism change form the second stage to the third stage are becoming better because the government has enhanced the administration and protection for water resources of the Boyang Lake.Finally,the paper makes a conclusion that mixed market mechanism that the government regulation combines with the market mechanism is the best mechanism for the Boyang Lake's water resources to be used and protected.