During drilling， when circulating drilling fluid flows axially in the wellbore ring， the circumferential motion occurs due to the rotation of drilling tools， and spiral flow is formed in the whole annulus. This may have a potential impact on the friction pressure drop in the annulus， especially the narrow gap. In this paper， the laminar flow under the rotation of concentric narrow gap ring drilling tools is calculated and analyzed by numerical simulation software. Among them， the drilling tool is ideal as drill pipe or cylinder， and the drilling fluid is composed of three kinds of Bingham fluid with different rheological parameters. The drilling fluid is the current numerical simulation results show that the PLR （pressure-loss ratio） is almost constant at different drilling tool/rod speeds； this indicates that the friction pressure drop in the annulus does not change significantly during the drilling tool/rod rotation； However， a comparison of some empirical formulas reveals that， with the exception of Ooms （1999） formula， which matches the current calculations， none of the other formulas can reflect the phenomenon. Moreover， by observing the radial variation of annulus pressure， the results show that the pressure is almost constant along the radial direction in the current 180rad/min range， and even when the rotational speed increases to 600 rad/min， the radial variation is very limited， accounting for about 2×10^-5 order of magnitude. therefore， in the current engineering application range （drilling tool speed within 180rad/min）， drilling tool rotation will neither cause an increase in axial friction pressure drop nor cause significant changes in pressure along the radial direction. The results of this paper provide some references for the estimation of friction pressure drop caused by rotating drilling tools in the actual drilling process， which can help to optimize the drilling process and equipment design， and improve the drilling efficiency and safety.