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Waste plastics have emerged as a global environmental issue. Polyethylene, accounting for about 25% of global plastic production, has been acknowledged as the major cause of "white pollution". In this paper, a generalized molecular-level kinetic model was proposed to understand the pyrolysis of polyethylene applying structure-oriented lumping, Poisson distribution, and genetic algorithm. The number of ordinary differential equations derived from the reaction kinetics were dramatically reduced by this simplified network with 14-rule design. The generalizability was confirmed by case studies without any change in the rule design. Under most conditions, the mean relative error between experimental and model data could be controlled within 5%, while abnormal deviations indicate the obstacle of heat transfer. The simulation curve could provide guidance for the experiments by locating the peak value of products. From 400–470 °C in Case 2, the increase in the reaction proportion of producing light oil explains the experimental results from the perspective of molecular-level reaction network. The comparison between PE and PS pyrolysis elaborates different pyrolysis mechanisms based on the different molecular structures. • Established a generalized molecular-level model for polyethylene pyrolysis. • Offered an efficient tool avoiding repeated work in pyrolysis simulation. • Confirmed the generalizability by case studies without changing the rule design. • Provided guidance for the experiments by locating the peak value of products. [ABSTRACT FROM AUTHOR]