A dynamic finite element model was established to characterize the motion state of the rotary steerable bottom hole assembly (RSBHA). Then the steering lateral force on bit was obtained after the motion equation was solved. The relation between the bit steering force and the pads offset pointing towards the high side direction of the borehole was gotten and the effects of the rotary speed on the bit lateral steering force were analyzed. Results showed that the near-bit stabilizer would contact the wellbore wall with the increasing of the pads offset, resulting in an inflection point presenting on the relation curve between the bit inclination force and the pads offset value. The larger pads offset value was, the more concentrated bit side cutting would be. Rotary speed had a small effect on time average of the bit lateral steering force but could enlarge the action range on both sides of the high side direction of the borehole.
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