Abstract: In a gas injection method for deep-layer strong bottom water reservoir, a plurality of gas injection mediums is provided for the present reservoir at issue, and a miscible feature of each gas injection medium in crude oil of the present reservoir is analyzed, so as to select a number of target gas injection mediums, which is combined with a well group simulation model corresponding to the present reservoir to obtain an optimal gas injection ratio between the target gas injection mediums. Based on the optimal gas injection ratio and the well group simulation model, gas injection simulation is performed for the present reservoir through a plurality of gas injection modes respectively to obtain an increment in recovery efficiency corresponding to each gas injection mode, thereby determining an optimal gas injection mode. Gas injection then is performed in the present reservoir through the optimal gas injection mode.