A new multistage countercurrent melt crystallizer with sieve plates is proposed that combines the advantages of the TNO column crystallizer and the inclined column crystallizer. With the naphthalene-indene solid solution system, the purification process of organic materials in the new multistage countercurrent melt crystallizer with sieve plates under total reflux was investigated. Two of the influencing factors on the separation and purification performance in the new multistage countercurrent melt crystallizer with sieve plates were crystal settling velocity and crystal breakage, which were controlled by stirring speed, the sieve plates, the angle of the sieve plates, the diameter of the pores, particle sedimentation area, and the number of plates. The results of this study show that the optimum stirring speed was determined to be 20 rpm, sieve plates can obviously increase the separation and purification effect, the optimum angle of the sieve plates was determined to be 45o, the optimum diameter of the pores was determined to be 8 mm, the optimum particle sedimentation area was determined to be 0.5 r, and two plates in the crystallizer were shown to be the best.