The invention relates to a method for separating organic macerals from source rock. Kerogen which contains rich organic matter and is separated from the source rock is ground to be in the granularity of 100-1,600 meshes and is then gradually separated with specific gravity liquids with increasing densities, and the macerals in different density ranges can be obtained. According to the method, the specific gravity liquid prepared from alcohol and a heavy fluid at a first separation density point of the first kind of organic macerals is adopted, the affinity of to-be-separated components and the specific gravity liquid is improved, and the maceral separation effect is improved. With the adoption of separation of the organic macerals in the source rock can be realized, the precise density range of the organic macerals can be obtained, and a basis is laid for rapid separation of a large quantity of organic macerals in the source rock.