The invention discloses a method for establishing an inter-well connectivity model. The method comprises: a step of determining initial model parameters, including based on geological parameters of a water injection well and a liquid producing well, calculating initial model parameters of the liquid producing well; a step of establishing an initial connectivity model, including based on the initial model parameters and a Dirichlet function, establishing an initial connectivity model between the water injection well and the liquid producing well; and a step of optimizing the model, including based on practical operation data of the water injection well and the liquid producing well, and the initial model parameters, solving a preset optimizing condition according to the Bayes theory combined with a projection gradient restriction optimization algorithm, to obtain optimized model parameters, and substituting the optimized model parameters into the initial connectivity model to obtain an optimized connectivity model which is used for inter-well connectivity analysis. The method can conveniently perform quantitative calculation on dynamic connectivity between the liquid producing well and the water injection well, and the method is high in calculation precision and reliable in result. The method has good practical application effect and application values.