Abstract: To obtain the fully developed laminar flow law in a rolling narrow rectangular duct,the forces on fluid particle within a moving coordinates frame was analyzed firstly,and the momentum equation under rolling condition was solved to get fully developed laminar velocity distribution and friction factor.Then,the isothermal laminar flow experiments with 900 ≤ Re ≤ 2600 under rolling condition with amplitude of ±15° and period of 8s were conducted.The research results show that the most difference between rolling and stationary conditions is that the pressure gradient varies periodically with each body force,thus hydro-dynamical structural relationship readjusts while the shear stress keeps constant;the pressure drop wave induced by each body force will results in the total pressure drop wave while the friction pressure drop and mass flow rate keep constant;the laminar friction factor under rolling condition also keep constant,and the theoretical prediction deviates from-1.1% to +4.3% in comparison with the experimental data,therefore both results are with a good agreement.