With the high-tech and multimedia society coming, monitor has become one of the most important peripheral in PC industry. The projector have advantages in characteristic of high luminance, color value and long product cycle etc, therefore it’s potential for development should not be disregard in the future. The research first introduces the display principles of the display and projector which are popular in the market. Second, we establish one practicable specification and makes gradual progress to complete optical analysis and optimize the f-theta scan lens for laser display system.