The invention discloses an underground angle measuring and calculating instrument. The underground angle measuring and calculating instrument is characterized in that a square scale surface is comprised; an angle dial (1) is arranged on the square scale surface through taking one right angle of the square scale surface as a circle center and taking the square side length as a radius, a dial centre point (2) is movably connected with a pointer (3) which can sag freely by self-gravity, and the two sides,opposite to the dial centre point, of the square scale surface are respectively provided with a vertical length dial (4) and a horizontal length dial (5); and the scale values of the vertical length dial (4) and the horizontal length dial (5) are values formed by uniformly dividing the edges of the dials into 100 equal parts, and the maximum scale value is arranged at the joint of the vertical length dial (4) and the horizontal length dial (5). By using the underground angle measuring and calculating instrument disclosed by the invention, the angle data can be directly measured, and the data relevant to angle function values can be timely and accurately read as well; and a situation that the technical personnel can learn design parameters and schemes only after calculating or inquiring information is broken.