Calculating the cyclone pressure drop, Delta p(c), at a high inlet solid concentration, C-s, in, is important for the design and operation of circulating fluidized bed boilers. Three typical Dpc models that consider the effect of C-s, in were selected and assessed. Compared with experimental results, it was found that only the model developed by Chen and Shi can correctly predict the variation trend of Delta p(c) with C-s, in at high values of C-s, in, but the predicted values are much greater than the measured values. It is suggested that the dissipative loss of swirling dynamic pressure should be excluded from the total dissipative loss of gas dynamic energy when the pressure tap is closely installed to the outlet and the swirl exponent could be assumed to be null for high C-s, in conditions. A set of equations modified from the original C-S model is given. Compared with the experimental data obtained from the present study and some data from literature, the improved C-S model can predict Delta p(c) at high C-s, in well. In addition, it was found that the correction of pressure tap position is more obvious than the correction of swirl exponent.