The invention provides a method and device for selective acidizing of a reservoir stratum. The method includes the steps of obtaining a geological connected graph of an oil reservoir; determining a first target oil layer and to-be-selected oil layers according to the geological connected graph and a first preset rule; picking the standard gas injection intensity of the oil layers, obtaining oil layer parameters in the to-be-selected oil layers, and obtaining the gas absorption percentages of the to-be-selected oil layers according to the oil layer parameters; determining the gas injection intensities of the to-be-selected oil layers according to the gas absorption percentages of the to-be-selected oil layers; calculating the difference values between the gas injection intensities of the to-be-selected oil layers and the standard gas injection intensity of the oil layers; obtaining specific values by comparing the difference values with the standard gas injection intensity of the oil layers; determining a second target oil layer and a third target oil layer according to the specific values and a second preset rule; blocking the third target oil layer and acidizing the first target oil layer and the second target oil layer; and unblocking the third target oil layer after finishing acidizing of the first target oil layer and the second target oil layer. The method and device provided by the invention can improve the acidizing effect on the reservoir stratum.