Shear transferring mechanism of the plasterboard wall reinforced with in-filled RC columns was studied. It is found that plasterboard ribs can transfer shear between in-filled RC columns effectively and have great effects on the behaviour of the composite wall. Equivalent slitted shear wall model is then presented. Slits are arranged on the equivalent shear wall to ensure it has same elastic lateral stiffness as the composite wall. Comparative analysis shows that plasterboard wall reinforced with in-filled RC columns has similar load bearing mechanism as the slitted shear wall and can be simulated by the proposed equivalent slitted shear wall for both elastic and plastic states.