The resource assessment of pyrolysis gas generated by dispersed liquid hydrocarbons involves 5 aspects, which can be summarized as “five steps methodology”. Firstly, the distribution ratio and amount of liquid hydrocarbon within and out of the source must be studied. The results of simulation experiments and statistical analysis on geological samples showed that a considerable number of hydrocarbons had been retained in source rocks while the quantity was controlled by various factors, including organic matter abundance, type and evolution degree, source rock’s lithology and source-reservoir allocation. Generally, the oil expulsion efficiency of different source rocks varied from 20% to 80%, and the data is less than 50% for source rocks with TOC lower 2% and more than 50% for those with high TOC (higher than 2%), which means that the source rocks with high organic matter abundance and excellent type will have high oil expulsion efficiency. Secondly, the distribution of major rich areas of dispersed liquid hydrocarbon inside and outside of the source rocks were studied through forward modeling and inversion method. The dominant migration pathway and distribution zone of the liquid hydrocarbons were conducted by numerical modeling while the distribution zone could also be tested through inversion method including statistics on thermogenic asphalt and fluorescence characteristics of reservoir samples. Thirdly, the conversion ratio of pyrolysis gas generated by liquid hydrocarbon of various occurrences should be known. Simulation experiments of gas cracking from dispersive liquid hydrocarbons mixed with carbonate, mudstone and sandstone showed that all of these three minerals had catalytic effect on the cracking process of liquid hydrocarbons, and their strength decreased one by one. The main gas generation periods of liquid hydrocarbons mixed with these three minerals are 1.2%~3.2%, 1.3%~3.4% and 1.4%~3.6% respectively. Moreover, overpressure could inhibit the process of gas generation. The mixture temperature lag is about 30℃ while comparing the experimental results of 200Mpa and 50Mpa. Fourthly, the study of petroleum system of the studied area, especially the analysis of key factors and critical moments for the late scale formation and accumulation of natural gas of the liquid hydrocarbon cracking gas. Fifthly, quantitative assessment and resource evaluation of pyrolysis gas generated by dispersed liquid hydrocarbon. The quantitative assessment method of “five steps”, which is based on genetic method, realized the integrated and systematic assessment of pyrolysis gas generated by dispersed liquid hydrocarbon inside and outside the source rock, by paleo-reservoirs, and degradation gas generated by kerogen.