The invention discloses a non-circular gear set and a transmission structure for a pump. The gear set comprises a drive gear, a first driven gear and a second driven gear, wherein the first driven gear and the second driven gear are arranged on the two sides of the drive gear and are of the same structure. The distance between a gear shaft of the first driven gear and a gear shaft of the drive gear is equal to the distance between a gear shaft of the second driven gear and a gear shaft of the drive gear. The transmission structure comprises a driving device, the gear set and a plunger. The driving device is connected with the drive gear in the gear set. Each of the two sides of the drive gear drives one corresponding driven gear. Each driven gear is connected with a connecting rod, and the connecting rod drives the plunger to reciprocate. The driven gears can be made to run stably through the non-circular gear set based on the non-circular gear set and the transmission structure for the pump, and stability of linear motion can be ensured when a crank block device is used for converting the circular motion of the gears into linear motion; and meanwhile by means of a transmission structure in the transmission structure for the pump, the flow pulse generated when the pump drains and outputs liquid can be obviously reduced.