The invention provides a device system structure and preparing method based on mixed crystal orientation SOI and channel stress. According to the preparing method, a (100)/(110) overall-situation mixed crystal SOI structure is prepared firstly, then a relaxation germanium silicon layer and a strain silicon layer are respectively extended on the overall-situation mixed crystal SOI structure, a (110) extending image window is formed, the surface of an imaging mixed crystal SOI structure is flattened after a (110) silicon layer and a non-relaxation germanium silicon layer are extended on the (110) extending image window, a separating structure for separating a device is formed, and finally, a P type high-voltage device structure is prepared at the (110) substrate portion, and a P type high-voltage device structure and/or a low-voltage device structure is prepared at a (100) substrate portion. Thus, carrier mobility of all devices is effectively improved, Rdson of high-voltage devices is improved, performance of all devices is improved, integration is further improved, and power consumption is further reduced.