The utility model provides a power supply device of a portable fruit power tool. The power supply device comprises a waistcoat, a shoulder belt connected to the upper end and the lower end of the waistcoat, a waistband connected to the left end and the right end of the waistcoat, and a waistcoat-like knapsack device composed of a battery pack bag and arranged on the rear portion of the waistcoat. A battery pack is arranged in the battery pack bag. The battery pack is connected to a power supply control device arranged on the waistband through a cable. The power supply control device comprises a control box, and such elements arranged on the control box as a power switch, a power output socket, a power-on indicator lamp and a lack-of-power indicator lamp. The power supply device has the advantages: the waistcoat-like knapsack device disperses the weight of the battery pack centralized at the waist in the past to each direction of the back, so that the labour intensity of an operator is reduced and the comfort of the operator is enhanced; and as the battery pack and the power supply control device employ a split type power supply structure, the operator can switch on the power of the battery pack more conveniently, and the safety factor is improved.