The Songliao basin contains rich resources of oil shales in the Upper Cretaceous Qingshankou (K2qn) and Nenjiang (K2n) formations, which has been identified 4 super-large deposits of middle-shallow oil shales. Oil shale resources present the characteristics of higher exploration in the local and lower recognition in the global region. We adopt a statistical analogy with the predominance of geological analogy and statistical algorithms to assess potential resources of oil shales, We selected a super-large deposit of oil shales as the calibrated region in southern Songliao basin of Jilin Province. Based on the metallogenic and enriching mechanisms of oil shales, main geological parameters are optimized to establish the data base of geological analogy. Those parameters are reset by a principle of qualitative transformation with multi-state. Moreover, an approach of characteristic factor is utilized to calculate the probability distribution function of analogical coefficients between the calibrated and predicted regions. Methods of monte-carlo and composite sampling are used to estimate potential resources of oil shales at different level of probability, based on constructed probability distribution function of volume abundance for oil shale resources. In this study, we firstly propose the principle of “high probability value with remarkable fluctuation” to select a reasonable probability range of potential resources. Oil shale resources from the probability range of 100% to 85% are taken as a reasonable result of resource assessment in the Nenjiang Formation of the Songliao basin. Our results show that potential resources of oil shales from the middle-shallow Nenjiang Formation are 296.72 gigaton (100%), 335.62 gigaton (95%), 383.40 gigaton (90%), and 430.77 gigaton (85%) (avg. 359.13 gigaton). Therefore, we establish a promising assessment system for predictive resources of wide range and low exploration, aiming at the insufficient approach of resource assessment in the middle-low exploration basin. Our technique may be utilized to attempt to assess the energy or mineral resource in the sedimentary basin of other same types.