The embodiments of the present disclosure provide a method, a system, and an application for detecting at least one of a cell-killing efficacy or an immune activity. The method comprises: obtaining a plurality of microscopic images of a fixed area of a co-culture sample, wherein the co-culture sample is a cell sample obtained by co-culturing target cells and effector cells, the fixed area of the co-culture sample includes a plurality of objects, wherein the plurality of objects are a cell group including cells with different properties, each of the plurality of objects having an image-identifiable feature; performing an image overlapping synthesis analysis or an image fusion analysis for the plurality of microscopic images to obtain the cell properties of the plurality of objects and make statistics to cell parameters associated with the cell properties; and evaluating at least one of the cell-killing efficacy or the immune activity of the effector cells based on the cell parameters.