The invention discloses an illuminating brightness adjusting method and an illuminating brightness adjusting device, an illuminating method and an illuminating device. The illuminating brightness adjusting method comprises steps: first operation by a user is detected, wherein the first operation is operation on a mobile terminal by the user; whether the first operation is flash opening operation is judged, a first judgment result is obtained; when the first judgment result shows that the first operation is the flash opening operation, a first instruction is sent to a light detector, wherein the first instruction is used for triggering the light detector to detect the illumination strength of the surrounding environment; the illumination strength result detected by the light detector is received; according to the illumination strength result, a first numerical value for driving current of a flash driver is determined; and a second instruction is sent to the flash driver, wherein the second instruction is used for controlling the flash driver to provide driving current for the flash according to the determined first numerical value.