This research focuses on the thin circular arc rotor airfoils at a low Reynolds number.A novel thin circular arc airfoil with a convex structure was designed in consideration of its demand for high aerodynamic performance,high structural strength,lightweighting and easy manufacture.A convex curve on the upper surface of the airfoil was adopted to increase the thickness of airfoil at the partial chord and a stiffener in the airfoil was installed to improve the structural strength of blade span wise.The designed thin circular arc airfoil has the maximum thickness of 4.3%,a circular average thickness of 2.5%,the maximum camber of 5.5% and an average camber of 4.5%.Numerical simulations for computing the aerodynamic performance of the airfoil were performed at the representative Reynoldsnumber between 40,000 and 100,000,and the angle of attack(AOA)from-4°to 12°by using the two dimensional steady and incompressible Navier-Stoke equations.The pressure coefficient distribution line of airfoil surfaces and the velocity vector were acquired.A carbon fiber rotor with a diameter of 40 cm,a mass of 15 g and rotor pitch of 15.7cm was manufactured with the present airfoil,and the experiments on the lift force and the structural strength in a hover state were performed and the results show the performance of the airfoil meets the use requirments.At present,the developed rotor airfoil has been successfully used in a rotor aircraft.