This paper presents a brief theortical analysis of the so-called three-element method，a short-cut formula for analyzing first-order networks，and then，applying the results to second-order networks，derelops some short-cut formulae for solving zero-input responses and zerostate responses in various cases. These formulae are referred to as six-element method. As in the case of three-element method，here one need not write any differential equations and make any differential and integral calculations. By making only some simple algebraic calculations，the responses of second-order networks can be obtained. For comparison，some examples are provided.