A new method of rapidly signing single-crystal electron diffraction patterns in the cubic system has been described in this paper. There Are two important features of single-crystal electron diffraction patterns in the cubic system; 1.Rectangular arrangement of spots; 2.There is a mathematical relationship between the two adjacent edges of the rectangle. The value of the above mentioned features has been listed in a table at the end of this paper. The patterns can be signed rapidly by means of the above mentioned table. This new method is simpler than any other traditional ones.