A nano coaxial rotor was designed, fabricated and studied experimentally at an ultra- low Reynolds number ranging from 5000 to 20,000. The Minimum Induced Loss theory was employed to optimize the geometry of nano coaxial rotor with the introduction of weights to take into account the interference of upper rotor and lower rotor. The chord and twist distributions of both rotors were achieved as a result. Nano coaxial rotor was then fabricated with a lightweight material of carbon laminate. Two rotor slices were obtained with mass less than 0.3 g and the thickness less than 0.23 mm. Successively, a sensitive test bench was designed to measure the hovering performance of nano coaxial rotor. Single upper rotor and lower rotor were tested with the test bench as well as the isolated upper rotor and lower rotor of nano coaxial rotor. It is found that the designed nano coaxial rotor can generate a thrust of 0.105 N with torque cancelled. And the comparison between single rotor and isolated rotor of nano rotor showed that the mutual interaction between rotors improves upper rotor performance but impairs lower rotor performance.