Titanium nitride (Ti-N) thin films were deposited by unbalanced magnetron sputtering under conditions of various N2 flow rates at room temperature. The morphologies and optical properties of the films were studied. Four layers of solar selective absorbing coatings based on Ti-N were designed and then optimized by optical design software of SCOUT. Results show that various characteristics such as bubble precipitates, bubble bursting, and amorphous morphologies are observed in the films with the increasing of N2 flow rate. The UV-Visible-NIF spectra show that the optical properties of the films can be improved using appropriate sputtering parameters and software optimization. Absorptance of the optimized films is enhanced from 0.8209 to 0.9048 after optimization, which are suitable as solar selective absorbing coatings