Abstract: An optical imaging system having a free-form surface includes an image source for generating image light, a lens assembly for reflecting the image light incident thereon, a first reflective surface, a second reflective surface, and a beam splitter that are disposed opposite to each other. The present disclosure allows the image light to pass through the lens assembly twice, reduces the weight of the optical system, and makes the system structure more compact, thus providing an optical imaging system featuring low distortion, high image quality, and a compact structure. A reflective surface is disposed between the image source and the lens assembly, so that the distance between the image source and the lens assembly can be reduced. The second reflective surface is designed as a free-form surface and a first lens and a second lens are aspheric lenses.