An adjustable parameter k was introduced in an original model based on Darcy's Law to increase its accuracy, and a new semi-empirical model predicting permeate flux for dead-end microfiltration (MF) systems was proposed. The adjustable parameter k was validated in laboratory experiments by using two different suspensions (kaolin and yeast). The membranes adopted in this research included flat PES and PVDF with 0.2 mu and 0.1 mu average pore size respectively. The experiments showed that this adjustable parameter was almost independent of operating conditions pressure, concentration and temperature), but depended on the character of the cake formed on the membrane surface and on the type of membrane. The average values of k for yeast and kaolin are 4.15 and 1.10 respectively. The results showed good agreement between model prediction and experimental observations.