Operation parameters restrict the performance of hydrocyclone in offshore platforms. Based on the computational fluid dynamics (CFD) software Fluent and the similarity parameter criterion experiment, the numerical simulation of the separation flow field and separation efficiency of hydrocyclone at different feed solid concentration was carried out, taking short circuit flow into account, a new correcting separation size equation was derived according to the locus of zero vertical velocity (LZVV) method. The results shown that when the feed solid concentration was more than 40%, the peak value of tangential velocity decreased and the increasing amplitude of underflow pressure drop will decrease compared with the increasing amplitude of overflow pressure drop, the region with the highest turbulence intensity increased when the concentration was more than 40%. The total separation efficiency and the feed solid concentration showed a positive correlation at 0 ~ 40%, and the increase in total separation efficiency was the smallest when it was higher than 40%, with a value of 0.63%. There was a large difference between the values of d50c* and d50c while the feed solid concentration was 50%. From the above results, it could be concluded that the optimum feed solid concentration ranges were 0 ~ 40%. The new correcting separation size equation could be used in the range of 0 ~ 40%. This study could have certain guiding significance for the field application of the offshore platform desanding hydrocyclone.