Gaussian operations are vital tools for constructing desired quantum networks in CV quantum protocols. As advanced quantum research evolves towards more complex scalable quantum networks, implementing multimode Gaussian opera- tion becomes essential. Not only for examining the unknown multimode Gaussian operation but also for controlling the multimode Gaussian operation, charac- terization of multimode Gaussian operation is required. Especially investigating multimode squeezing operation is crucial since it generates nonclassical behav- ior, inducing the quantum advantages. Prior investigations have been conducted only on the multimode linear Gaussian operation. However, in this paper, we experimentally obtained complete information on multimode Gaussian opera- tion, including multimode squeezing operation. With the new method of using coherent and vacuum probe, the transfer matrix T and the noise matrix N was obtained. Characterizing the noise matrix N enables us to determine the noise during the process, working similarly to an indicator of a decoherence-free sub- space. Our method can be further used in many quantum protocols, especially for quantum information processing.