Provided is a method for rapidly and effectively measuring the importance of circuit units. The method comprises a step 1 of analyzing a netlist and initializing a correlative, 1.1) reading a circuit netlist, 1.2) detecting the interconnection structure between circuit units and displaying an implicit series-parallel connection relation, and layering a circuit by using a hierarchical algorithm; a step 2 of computing the reliability change gradient [epsilon] of the circuit units; a step 3 of outputting the circuit units ordered according to importance in order to use the circuit units as a design basis, 3.1) ordering the <g, [epsilon]> in an ascending order of the [epsilon], 3.2) ordering the circuit units with same [epsilon] according to the coverage rates of sensitization pathways, 3.3) successively extracting, from the <g, [epsilon]>, corresponding circuit units g to be used by a circuit designer. The method is high in measurement precision, low in computation complexity, and good in maneuverability.