The integrity verification system includes a client and an RCE server. The client requests an RCE service to the RCE server using a pointer of a return function as a parameter of a service call function and transmits a memory code of the return function to the RCE server when Reverse-RCE for obtaining the memory code of the return function is requested from the RCE server. The RCE server generates a first hash key of the transmitted memory code, compares the first hash key to a stored second hash key of the memory code of an original return function, generates a return value according to a compared result between the first hash key and the second hash key and transmits the generated return value to the client using the generated return value as a parameter of the service call function. The client executes the return function using the return value as a parameter of the return function.