We carried out molecular dynamics simulations to study the crystallization of long polymers in a concentrated solution made by an explicit solvent of short chains. The weight- averaged entanglement length in the concentrated solution is found to exhibit power-law behavior with respect to the polymer volume fraction. The crystalline stem length obtained by quenching the solutions below melting temperature displays a linear relation with the entanglement length in the homogeneous solution above the crystallization temperature. Chain folding numbers are found to be very dose to those in pure melts at different initial temperatures, and they tend to moderately decrease with increasing concentration of the long polymers. While our results are directly obtained from a coarse-grained model, they seem to suggest that the topological restriction of entanglements is a universal property to control the thickness selection during polymer crystallization.