This paper presents Hirschorn's algorithm (decoupling and linearization algorithm) for a approximated model of interacting thermal non-linear process. Closed loop simulation was carried out incorporating the above algorithm and the results are compared. Control performance of a Hirschorn's is found to give better results. Obtained control laws for Hirschorn's algorithm shows relatively good results. The control laws obtained for Hirchorn's algorithm gives improved Settling time (Ts) and Integral Square Error (ISE). © 2012 IEEE.