The invention discloses a quantitative evaluation method for lateral sealing of a fault.The method is mainly based on the research about the fault sealing mechanism and influence factors thereof, under the circumstance that pressure bearing time of the fault is considered, a fault-reservoir displacement pressure difference method for quantitative evaluation of fault sealing is improved, and a fault sealing quantitative evaluation geological and teaching model taking the time factors into consideration is established.The gradual-approximation algorithm with the given step length is adopted, it is determined that rocks of a surrounding rock stratum have the same shale content as a target spot stratum and the burial depth at the diagenetic degree, then according to the relation between the product of the shale content of the rocks built in a research area and the burial depth and the displacement pressure, the displacement pressure of target spot stratum rocks is calculated quantitatively and compared with the displacement pressure of a target disc reservoir stratum, and whether the fault is sealed or not as well as the magnitude of the sealing capability are evaluated quantitatively.It is verified through actual data that when compared with a fault rock shale content (SGR) method and the fault-reservoir displacement pressure difference fault sealing evaluation method which does not consider pressure bearing time, the method has feasibility.