Study on Response to Zero Input of the Second Order RLC Circuit Based on Matlab Xie Zurong Che Yong Huang Zhichu Information Engineering College, Beijing Institute of Petro chemical Technology,Beijing 102600,China.Through the application of Matlab software a thorough analysis has been done on response to zero input of the second order series circuit of RLC discharge. The function relation between the peak value of impulse discharge current expressed as im and the other parameters, such as R,L,C respectively, has also been presented when R>?<2L/C respectively. Meanwhile, based on the calculation and plotting the article proves the consistency of various formula such as i m= f(R,L,C), i=f(t) and u c= f(t) when respectively. In the end,the article introduces and validates a sort of method to seek for im by using the theory of conservation of energy.matlab ;\ second order circuit;\ response to zero input