Tuning Proportional Integral and Derivative (PID) controllers for unstable Second Order Plus Time Delay systems with a Zero (SOPTDZ), based on internal model control (IMC) and stability analysis (SA) principles is proposed. The controllers designed by the proposed methods are used to control unstable jacketed Continuous Stirred Tank Reactors (CSTR), carrying out irreversible first order reaction. The performance of proposed controllers is compared with the synthesis method. Simulation results on nonlinear unstable continuous stirred tank reactors and transfer function models are presented to the show the efficiency of the proposed controllers.