With the rapid development of intensive livestock and poultry industry, a large amount of livestock and poultry manure is produced every year in China, which will cause environment pollution and a great waste of resources if not treated properly. Deep processing and utilization of livestock and poultry manure is required to achieve the “waste to treasure” change. Solid-liquid separation is an important procedure for the comprehensive utilization of livestock manure. In order to analyze how the dewatering performance of the interrupted-whorl screw separator was affected by different gap distance parameters, an Euler-Euler two fluid model was adopted to conduct numerical simulations of the interrupted-whorl screw with 20mm, 35mm and 50mm of gap distance. Work performances of the dewatering device in different gap distance scenarios were compared as well as the flow distribution of particle volume fraction, particle velocity distribution and the pressure distribution inside and outside the porous media region. Results showed that the numerical simulation can accurately reflect the internal flow characteristics of the interrupted-whorl screw extruding device. Working efficiency of the continuous extrusion dehydration device was decreased most by 7.9% with gap distance of 50mm. The volume fraction of cinder particles was decreased by 3.2% when the gap distance was shortened to 20mm. The variations of volume fraction changes in the runner were divided into three stages. The volume fraction was increased with a wavy shape in general and the gap length played an important role in influence on the flow pattern inside the cavity. The discontinuous zone had a certain buffering effect on the particle motion, and the length of the interval can control the retention time of particles in the cavity. The differential pressure inside and outside porous media areas had the largest growth in the late of dehydration. The smaller the gap distance under the same condition was, the greater the pressure difference became. By simulation, the optimal interrupted distance, the pressure on slag notch and speed was found to be 35mm, 5000Pa and 50r/min, respectively. This study can provide reference for the design of the spiral extrusion dewatering device.