The invention discloses a diamond achieving a ten-heart and ten-crown effect inside and a machining method thereof. The diamond comprises a top part, a waist part and a bottom part, wherein the top part comprises a carving surface, ten top triangular surfaces, twenty upper waist triangular surfaces and twenty triangular main top surfaces; every two adjacent triangular main top surfaces are upwards intersected to form a first edge, and an included angle alpha between the two triangular main top surfaces is equal to 162 +/- 0.5 degrees; when the diamond is exposed in light rays, two adjacent triangular main top surfaces and each top triangular surface show a first auxiliary arrow and a second auxiliary arrow which are symmetrically formed on two sides of a corresponding main arrow; and the first auxiliary arrow, the second auxiliary arrow and the main arrow jointly form a crown shape.