In the description and design of certain kinds of sequential machines, we often meet inadequacies of traditional models we adopt to use. To Lessen these inconveniencies, this paper aims to define polymachine as a new basic model of sequential machine. Polymachine, defind on the level of state model, is composed of an index which is and independent componet and a polymer which, as a dependent component, consists of many element machines. In the meantime, some basic characters of the machine are illustrated and discussed in detail, in order to present the usefulness of polymachine.