Waterflooding has been proved one of the most effective IOR method for mature field. Commingle waterflooding may result in quick breakthrough. Zonal water injection is used to decrease water-cut rise. Our aim is to make zonal flowrate constant. However, zonal flowrate usually change duo to reservoir feature and inter-layer influence. Also wellhead pressure change frequently which lead to flowrate change a lot. This paper introduces a new downhole constant flow nozzle which can keep zonal flowrate constant under the condition of pressure change. And the flowrate can be adjustable on line by instrument and then the nozzle can also keep current flowrate constant at that opening position. In this paper, a downhole constant flow nozzle in waterflooding wells is introduced. A constant nozzle is placed in each layer permanently. The nozzle has two chokes. One is used to adjust flowrate on line by instrument. The other choke is used for automatic flowrate control. The nozzle can keep flowrate constant by adjusting the opening of the choke automatically. The nozzle was also composed of arm, adjusting mechanism and two chokes. The effect of flowrate automatically control can be checked by instrument controlled by cable. The downhole constant flow nozzle has been implemented in the simulation well in jidong, PetroChina. It can realize two things. The first one is that the nozzle keep flowrate constant when tubing pressure change. Tests have been done at different position where the flowrate was adjusted from 10 to 50m3/d. Then pressure was changed from 1MPa to 10MPa. The lab test results show that the flowrate can be kept constant automatically within the accuracy 10%. In Jidong, if the accuracy can be controlled within 20%, it can meet the need of water allocation scheme. The chief merit of the nozzle is that it can not only be adjustable through instrument, but also can keep flowrate constant at any opening position. Even if the constant nozzle fails to work, the nozzle can still finish normal water injection. The test and adjustment efficiency can be improved by 15% by using this nozzle for waterflooding wells.