Accurately predicting pressure gradient with inner pipe rotation in concentric or eccentric annuli can provide theoretical foundation to evaluate equivalent mud weight for avoiding donwhole problems caused by overlarge donwhole pressure, such as: gas kick, lost circulation, even blowout. Nowadays, a lot of studies were carried out on basis of theoretical and experimental researches, however, to the best of our knowledge, no simplified model has been reported to predicting pressure gradient in concentric annuli with inner pipe rotation for yield-power-law (YPL) fluids. A Simplified modeling of laminar helical flow in concentric annulus with YPL fluids has been established on basis of numerical results. In addition, the validation of simplified model has been investigated by comparing results with computational fluid dynamic (CFD) simulations and experimental studies. Predictions of simplified model shown good agreement with CFD and experimental results only within ±5% error bars for power-law and YPL fluids in eccentric annuli.