Inlet configuration is important parameter of hydrocyclones,which has great impact on the classification performance.The effects of inlet configuration on the precise classification were studied by computational fluid dynamics under variouscombinations of inlet diameter and inlet velocity.The results showed that a high sharpness of classification was achieved withspecific inlet diameter and inlet velocity.The separation efficiency of the coarse particles by underflow significantly decreased wheninlet had an oversize diameter owing to a stronger short-circuit flow.It is resulted from the chaotic flow and the stronger pressuregradient around the vortex finder.Meanwhile,a low separation efficiency of the fine particles by overflow was achieved when inletvelocity was high,which indicated a low sharpness caused by the overlarge centrifugal force.