A control method of a display module, a display module, and a display device. The display module comprises: a transparent display panel (11) comprising an active area and a peripheral area, wherein the transparent display panel (11) has a display side; a dimming panel (12) disposed at a side of the transparent display panel (11) away from the display side; a light-intensity detection unit comprising a photosensitive sensor (13), wherein the photosensitive sensor (13) is disposed at a side of the transparent display panel (11) away from the display side and disposed corresponding to the peripheral area, and the light-intensity detection unit is configured to detect an incident-light intensity of an incident light; and a control unit (14) connected to the light-intensity detection unit and the dimming panel (12), respectively, and configured to adjust a transmittance of the dimming panel (12) according to the incident-light intensity.