The invention discloses a simple and practical measuring method of the dynamic unbalance amount of a fan. The method comprises steps as follows: 1), a to-be-measured fan is horizontally positioned by four elastic ropes, acceleration sensors are sequentially arranged in two adjacent quadrant positions of the to-be-measured fan, the to-be-measured fan is opened, and aX and ay are measured; 2), Newton laws of mechanics are adopted as follows: delta mrw<2> is equal to F which is equal to Ma, wherein r represents the radius of a fan blade, W represents the angular velocity of the fan and is shown as the specification, M represents the mass of the fan, a represents the accelerated velocity of the fan and is shown as the specification, by means of the formula, the dynamic unbalance amount of the fan is obtained as the specification M represents the mass of the fan, and n represents the rotating speed of the fan; and 3), ax and ay of the step 1) are substituted into the formula (I), and the dynamic unbalance amount of the to-be-measured fan can be calculated.