The utility model discloses a multifunctional concrete trowelling and galling tool for construction. The device comprises a flat plate, a magnetic panel is arranged at the top of the flat plate, a plurality of fixing blocks are equidistantly welded to the edge of the front surface of the flat plate in the vertical direction, a rotating shaft penetrates through the multiple fixing blocks, and galling grabbing rods are fixedly connected to the positions, between every two fixing blocks, of the outer surface of the rotating shaft. According to the utility model, firstly, a plurality of galling grabbing rods are turned downwards through a rotating shaft; the roughening operation on the concrete surface is convenient; the napping grab bars are turned upwards; therefore, the trowelling work of the concrete surface is facilitated; secondly, through a magnetic panel made of a magnet material at the top of a flat plate, a balancing weight is attracted conveniently to increase the pressure intensity, so that the trowelling effect of construction is guaranteed during trowelling work, and through sliding sleeving of a supporting rod and a supporting plate, the height of the tool is adjusted conveniently, and the tool has the effects of being convenient to store and carry.