Embodiments of the present disclosure provide methods and apparatuses for detecting an ambient light illuminance and for computing a correction coefficient, and an electronic device. The method for detecting an ambient light illuminance includes: filtering ambient light based on a monochromatic channel, such that a quantum efficiency curve of the filtered light matches a spectral luminous efficiency curve; and performing photoelectric detection on the filtered light to obtain an illuminance level of the ambient light. In solutions of the embodiments of the present disclosure, the photoelectric detection may be equivalent to obtaining an illuminance level of light by convolutional computation based on a spectral luminous efficiency curve, and therefore, when the quantum efficiency curve for a monochromatic waveband obtained by filtering ambient light based on a monochromatic channel matches the spectral luminous efficiency curve, a reliable spectral luminous efficiency curve can be obtained with a small computing workload.