The Contra-Rotating Open Rotor (CROR) design confronts significant noise challenges despite being one of the possible options for future green aeroengines. To efficiently estimate the noise emitted from a CROR, a three-dimensional unsteady prediction model based on the meshless method is presented. The unsteady wake flow and the aerodynamic load fluctuations on the blade are solved through the viscous vortex particle method, the blade element momentum theory and vortex lattice method. Then, the acoustic field is obtained through the Farassat’s formulation 1A. Validation of this method is conducted on a CROR, and a mesh-based method, e.g., Nonlinear Harmonic (NLH) method, is also employed for comparison. It is found that the presented method is three times faster than NLH method while maintaining a comparable precision. A thorough parametric analysis is also carried out to illustrate the effects of rotational speed, rotor-rotor spacing and rear rotor diameter on the noise level. The rotor speed is found to be the most influencing factor, and by optimizing the speed difference between the front and rear rotors, a notable noise reduction can be expected. The current findings not only contribute to a deeper comprehension of the CROR’s aeroacoustic properties but also offer an effective tool for engineering applications.