Abstract: The noise level distribution probability models of the USRK and KSRS arrays are derived from the observed data of the two arrays which belongs to the International Monitoring System (IMS) Arrays. Based on the scaling model of source spectrum of underground explosion, amplitudes of seismic wave signal excited by the second North Korean nuclear test on May 25, 2009 and recorded by these two arrays are scaled to amplitudes of smaller underground explosions with lower magnitude. Thus, the amplitudes of the North Korean nuclear tests with lower magnitude are obtained. By the probabilistic model method, the detection capabilities of these two arrays for seismic signal from Korean nuclear tests with different magnitudes are given in the multi-band on the condition that signal-to-noise ratio is greater than three. The result indicates that the detection threshold is reduced with the frequency increasing at these two arrays on the condition epicentral distance within 400−500 km. Capability in the high frequency is much stronger than that in the low frequency. In the band of 6.0−9.0 Hz, the detection thresholds of the USRK and KSRS arrays arem_b1.5 and m_b2.2 respectively in the 90% detection probability.