Abstract: In order to provide guidance for parameter settings in different error rate predicting models and for anti-irradiation hardened design, a 32-bit microprocessor is selected as our target circuit, and the sensitive depth of circuit is investigated. Utilizing the regional radiation of laser pulses and the adjustability of laser focus panel, we obtain the sensitive depth of cache areas, regfile areas and the combinational logic areas which are fabricated in 180 nm CMOS technology. Results show that the sensitive depth of the different sensitive areas in one device is almost the same whose value is about 1 μm. Sensitive parameters of the device can be obtained by this approach accurately, conveniently and fast which provide a strong reference to the device for better estimation of the error rate.