Abstract: The canonical form of multivariable linear system are determined by a set of invariants. For a given system, there may be several sets of invariants, therefore different canonical form, in essence, can be obtained. In this paper the nice selector determining the set of invariants has been discussed and a new conception of the nice selective pattern determining the nice selector has been proposed. We put stress on discussion of the natural nice selective pattern and the related canonical form, and made some comparisons with the well known Popov's canonical form. Finally, a identification algorithm have been given for identifing the canonical form corresponding to natural nice selective pattern.