In order to improve the security, reliability and economy of interruptible load undertaking market reserve during peak period, we establish a selection assessment model on interruptible load participating in market reserve during peak period and a benefit measurement model for Grid Company. In the aspects of security, reliability and economy, four main selection indices such as response time and reduction in system’s power shortage, etc. are selected based on probabilistic production simulation technique. By means of TOPSIS method, interruptible load’s characteristic in advantage and disadvantage is comprehensively assessed. Grid Company’s benefit is measured after preferentially purchasing a part of interruptible loads to undertake market reserve during peak period. The results of calculation instance demonstrate that the selection assessment model can distinguish each interruptible load’s difference very well in terms of security, reliability and economy and improve system’s power supply reliability and economy. Therefore, the science and validity of the model are verified.