Integration of multi-constellation GNSS creates a significant increase in the number of visible satellites,thus bring new opportunities for improving the accuracy and reliability of Real Time Kinematic (RTK) positioning.This paper proposes a reliableRTK positioning method based on partial wide-lane ambiguity resolution (AR) fromGPS/GLONASS/BDS (G/R/C) combination.It takes advantage that wide-lane observation has much longer wavelength,and the multi-constellation combined wide-lane ambiguity-fixed observations are directly used to positioning calculation.In the paper,the G/R/C geometry-based wide-lane ambiguity resolution models are unified and combined.Then a partial ambiguity resolution (PAR) method is introduced to avoid the influence of extreme errors from low-elevation satellites.A set real G/R/C baseline data is used as typical example to reflect the benefits of the proposed method.Experiment results show that the multi-constellation combination can significantly improve the wide-lane AR effects,including the AR success rate,ratio and initializationspeed.And the proposed PAR method can effectively avoid the negative influence of new-rising satellites.The positioning accuracy using the proposed method can still reach centimetre level.