The present invention provides a method and apparatus for generating a high dynamic range image (HDRI). After acquiring a first illuminance diagram, a base layer and detail layers are extracted from the first illuminance diagram, where the base layer contains low frequency information of the first illuminance diagram and the detail layers contain high frequency information of the first illuminance diagram. The dynamic range of the base layer is then compressed while dynamic ranges of the detail layers remain uncompressed. Further, a second illuminance diagram is generated from the first illuminance diagram by fusing the base layer with the compressed dynamic range and the detail layers, the second illuminance diagram is mapped onto a plurality of preset color channels; and the images on the plurality of preset color channels are fused into the HDRI. Therefore, the detail information in the original illuminance diagram can be preserved.