The embodiments of the disclosure provide an optical system and an image enlargement device. The optical system may include a display and an optical component disposed between the display and a viewing position. The optical component may include a first reflective element and a second reflective element. The first reflective element is configured to receive an incident light emitted from the display. The second reflective element is disposed on a reflected light path of the first reflective element, and configured to receive the incident light reflected by the first reflective element and reflect the reflected incident light to a viewing position. The first reflective element and/or the second reflective element having a function of concentrating light. Therefore, when the user looks at a display of a mobile phone or a terminal, the display is enlarged by the even reflection of the first reflective element and the second reflective element, thereby improving the user experience and comfort.