The invention relates to the field of hard material grinding equipment, in particular to a planetary gear train type grinding machine capable of realizing direction-changing speed adjustment. The planetary gear train type grinding machine comprises a stand and a planetary gear train mechanism, a grinding mechanism and a direction-changing driving mechanism which are arranged on the stand, wherein the planetary gear train mechanism comprises a working table; an inner gear ring, a sun wheel rotating shaft, a first sun wheel, a second sun wheel and multiple planetary wheels are arranged on the working table; the grinding mechanism comprises a rotating shaft; a rotating platform is arranged on the rotating shaft; a grinding wheel is arranged on the rotating platform; the direction-changing driving mechanism comprises a wheel carrier and a driving wheel, a first idle wheel and a second idle wheel which are arranged on the wheel carrier in a rotatable manner; and a handle for connecting the first idle wheel or the second idle wheel to the second sun wheel in a transmission manner by rotating the wheel carrier. The planetary gear train type grinding machine can effectively overcome the shortcomings that the main shaft of the conventional grinding machine is high in speed, the grinding amount is difficult to control, grinding is not uniform, and operation is difficult; and furthermore, the planetary gear train type grinding machine further has the characteristics of simple structure, relatively low manufacturing cost, easiness for maintenance, convenience for operation and the like.