For the urban resident, the park is very important and it can regulate breathing, balance pressure in our life, like the heart of the city. Now the underground spaces are more and more, but the problem of abandoned underground spaces have also been generating. Thus, in this project, the park will be set up under the ground. For lush greenery, sufficient sunlight and air are the most important and one of the great challenges of underground parks. With the concave lens and the convex lens, the use of light allows sunlight to be introduced into the ground so that there is enough natural light in the underground space and providing the wavelength and light source required for the photosynthesis of plants under the ground and use light to produce convection on the air, so that the park under the ground to achieve the best sunshine and air.