The invention relates to an optimization cascade bi-stability based weak transient zero sequence current characteristics extracting method which is aimed to obtain characteristic current of a weak transient zero sequence current fault under a background with heavy noise. The method is performed through the following steps: 1) building a two-level cascade bi-stability system X2; taking potential function parameters a1, b1, a2 and b2 in the two-level cascade bi-stability system X2 as optimizing objects; 2) optimizing the potential function parameters a1, b1, a2 and b2 in an expression for the two-level cascade bi-stability system X2 through an improved quantum heredity algorithm; outputting the best optimized parameters of a1J, b1J, a2J, and b2J; and 3) under the conditions of best optimized parameters and a variable metric method, using a fourth-order Runge-Kutta algorithm to solve the two-level cascade bi-stability system to obtain an outputted signal iT (t) of the two-level cascade bi-stability system under the variable metric method wherein signal iT (t) is the characteristic current of a weak transient zero sequence current fault. Compared to the prior art, the method is self-adaptive and suitable for use in conditions with heavy noise.