Against the background of data explosion and cloud computing, this paper investigates a branch of the cloud computing technology which is known as VDI (virtual desktop infrastructure). Users can access data and information via cloud desktops with the endpoint devices. The paper studies OpenStack - a famous open-source cloud platform which has been widely used, and introduces a secure, optimized and high-available VDI system based on it. The system provides responsive and highavailable desktop connections by multi-thread VM operating, enhances the security of the user-login process by security labels and device authentication.