The invention discloses a variable gear pump and a working method thereof. The variable gear pump comprises two gears which are placed in a shell, wherein the two gears are meshed; an upper limiting groove and a lower limiting groove are formed between each tooth root and each tooth of each gear; a steel sheet for adjusting the opening degree of the adjacent teeth is arranged between the adjacent teeth of each gear; each steel sheet can slide between the upper limiting groove and the lower limiting groove; and a driving device for controlling telescoping of the steel sheet is arranged at the bottom of each steel sheet. Telescoping of the steel sheet is controlled by the driving device, so that the output flow of the gear pump is changed between zero flow and full flow and different working condition requirements can be met. The variable gear pump is transformed and updated on the basis of the existing gear pump and has the characteristics of simple structure and easiness in manufacturing.