1. A control system for a plant, comprising: identifying means for identifying a model parameter vector of a controlled object model obtained by modeling said plant; and a controller for controlling said plant using the model parameter vector identified by said identifying means; said identifying means including: identifying error calculating means for calculating an identifying error of the model parameter vector; updating vector calculating means for calculating an updating vector according to the identifying error, the updating vector having at least one first element relevant to an input or an output of said plant, and a second element irrelevant to the input and the output of said plant; and updating vector correcting means for correcting the updating vector by multiplying a past value of the at least one first element of said updating vector by a predetermined value between about “0” and about “1”, and multiplying a past value of the second element of said updating vector by a value of about “1”; wherein said identifying means calculates the model parameter vector by adding the corrected updating vector to a reference vector of the model parameter vector.