Based on un-differenced model of clock estimation,the mathematic model of real-time clock estimation influenced by orbit error is derived,and then the estimation accuracy of BDS real-time clock and real-time positioning accuracy are analyzed.The results show that real-time BDS clock accuracy achieves 0.30ns using the rapid orbit product and the corresponding 2-D and 3-D real-time positioning accuracy are 0.36m and 0.48m respectively.With 0.1m and 0.2m orbit error influenced,the decreased accuracy of real-time clock estimation is 0.05ns and 0.14ns,and the decreased positioning accuracy is 0.057m and 0.154mrespectively.