In this paper we present an interactive aerial projection of 3D hologram objects by using the pyramid hologram and parabolic mirror system (for 3D hologram object reconstruction) and the Leap Motion sensor (as a finger movement detector of a user). This system not only can reconstruct and project the 3D hologram object in the mid-air, but also provides a way to interact with it by moving a user's finger. There are three main steps: the reconstruction of 3D object, the projection of 3D hologram object in the mid-air, and the interactive manipulation of 3D hologram object. The first step is realized by using pyramid hologram with LCD display. The second step is achieved with the parabolic mirror hologram. And Leap Motion sensor is used for the last step to detect user finger movement. This paper traces the design concept and confirms the system function of an interactive aerial projection of 3D hologram objects by a prototype demonstration.