To improve the separation efficiency of parallel hydrocyclones, a new type of common liquid hopper was designed. The separation efficiency of conventional parallel hydrocyclones and those parallel with liquid hoppers were measured experimentally and the influence of common liquid hopper on the flow field analyzed using FLUENT software. The results showed that the efficiency of the parallel hydrocyclones group with liquid hoppers was higher than that of the conventional group, with the maximum efficiency increased by 2.2% and average efficiency increased by 2.1%. The fishhook effect in the efficiency curves was clearly weakened. The separation efficiency of particles between 3 and 10 μm was clearly improved. Compared with the conventional parallel connection, a liquid hopper made the air core in the parallel hydrocyclone group disappear. Meanwhile. the locus of zero vertical velocities was closer to the inside of the hydrocyclone and the free vortex height higher, which make the separation space larger. In addition, parallel vortices in the liquid hopper possessed an inherent self-stability and restricted each other, which caused the swing amplitude of the vortex system center with liquid hopper to be smaller than that of the single vortex center. Therefore, it was demonstrated here that the common liquid hopper improved the separation efficiency of parallel hydrocyclones. Display omitted •Design a new type of parallel hydrocyclones with common liquid hopper.•The common liquid hopper can improve the separation efficiency.•The common liquid hopper eliminates the air core and make separation space larger.•The common liquid hopper makes self-stability of the vortex system stronger.