With the rapid development of cloud computing platform

the traditional network architecture can not meet our demands.The centralized control of data planes realized by the Software Defined Network（SDN）-based technology has become the evolution trend of the current network technologies.This paper first briefly introduces the design of the OpenFlow switch on the basis of such technologies as OpenFlow and OpenStack and the building of an OpenStack-based IaaS cloud management platform which further converges the advantages of SDN and cloud computing.Then

it presents a method of SDN simulation on the cloud computing platform

which can simulate the actual SDN and use the simulated network toevaluate the network performance

thus optimizing the design and reducing the input for SDN planning and construction.