The invention discloses a preperitoneal space separator. The preperitoneal space separator comprises a separator body, wherein a handle, a guide bar and an inflation device are arranged on the separator body; an inflation tube is arranged in the guide bar; a dilation balloon is arranged at the front end of the inflation tube; the rear end of the inflation tube is connected with the inflation device. According to the preperitoneal space separator, owing to the handle and the guide bar, surgical operations under laparoscopes are facilitated; the inflation tube arranged in a front and back sliding manner can stretch and be positioned as required, and the dilation balloon can change directions along with a steering bar to adapt to all situations in the operations; the inflation structure can adopt an inflation balloon or an air inflating device, so that the preperitoneal space separator is simple in integral structure and convenient to operate.