Realizing a large-scale fully controllable quantum system is a challenging task in current physical research and has broad applications. In this work, we create a reconfigurable optically levitated nanoparticle array in vacuum. Our optically levitated nanoparticle array allows full control of individual nanoparticles to form an arbitrary pattern and detect their motion. As a concrete example, we choose two nanoparticles without rotation signals from an array to synthesize a nanodumbbell in situ by merging them into one trap. The nanodumbbell synthesized in situ can rotate beyond 1 GHz. Our work provides a platform for studying macroscopic many-body physics and quantum sensing.