An illumination system, an illumination control method and a projection apparatus are provided. The illumination system includes a first laser light source providing a first laser beam, and a light splitting module. When the first laser beam is incident to the light splitting module, a first portion of the first laser beam penetrates through the light splitting module, a second portion is reflected by the light splitting module. In the first illumination mode, the first laser beam is incident to the first light splitting region to form a first proportion of the first portion and the second portion. In the second illumination mode, the first laser beam is incident to the first light splitting region to form a second proportion of the first portion and the second portion, wherein the first proportion and the second proportion are different.