The invention relates to a horizontal grinding mill with built-in classifying turbine, the technical solution of which is that a grinding chamber [18] is filled with grinding medium [6], a medium discharging valve [20] is installed on the middle of the bottom of a cylinder [7], a feeding pipe [10] is above a right end cover [9] of the grinding chamber [18] and a medium discharging pipe [2] is concentrically communicated with the grinding chamber [18] by a left end cover [3]. The length of the cylinder [7] is 1.5 to 2.5 times of the diameter thereof. A fairing [4] is fixedly installed on the left end cover [3] of the grinding chamber [18]. A classifying turbine [5] is vertically installed on the left end of a spindle [13]. A clearance between the classifying turbine [5] and the left end cover [3] is 5mm to 10mm. Five to eight mixing turbines [8] are vertically installed on the spindle [13]. The distance between the mixing turbines [8] decreases gradually from left to right and the right distance is 0.9 to 0.95 times of the left distance. The right end of the spindle [13] is connected with a driving mechanism by the right end cover [9] and a sealing device [11]. The invention has low starting power and can grind and classify with a function of selectively grinding.