Research on Object Function of Optimal Parameters for controllers HE Jinyuan 1 ZHOU Guopeng2,3 (1.Network Center of Xianning college, Xianning, Hubei, China , 437005; 2. Mathematic department of Xianning college, Xianning, Hubei, China , 437005; 3. College of Automation Science & Engineering , South China University of Technology, Guangzhou, Guangdong , China, 510641) Abstract:The parameter optimization of control systems always refers to different object functions. The propose is that the selected object function should exactly reflect the characteristic of the control system, while making the computation easy. In this paper we combine simplex search of optimization technique and optimization toolbox in Matlab confirm that "ISE" principle has some problems while using it as our object function. By the means of theory analysis based on optimization, we propose a new object function, which improve the time domain performance evaluation (such as overshoot and adjustment time). Key Words:Simplex search; Object function; Parameter optimization