A new collection efficiency model for PV cyclones under high inlet solids loading is proposed based on the Muschelknautz model.The separation space is divided into two regions，particle controlling region near the wall and gas controlling region in the center.The tandem separation model is used for the first and second separation processes of the cyclone operated under high inlet solids loading.When the inlet concentration is higher than the critical concentration，there are two regions in the cyclone.In the particle controlling region，the particles velocity is larger than the gas velocity and all the particles are collected，which is the first separation stage.In the gas controlling region，the particles velocity is less than the gas velocity，so that the particles are collected by centrifugal force，which is the second separation stage.The total separation efficiency is the sum of the efficiencies in the two stages.The results by tandem separation model are in agreement with the experimental results for the inlet concentration in the range of 0.002—1 kg·m-3.It is shown that the critical concentration has a significant effect on the calculation for the total efficiency.In the tandem separation model，the structure factors and particle properties are taken into account，which meets the requirement of engineering design and calculation.design and calculation.