Abstract: TNPS units 3 & 4 loaded TVS-2M fuel assemblies from the first cycle with transiting from year fuel cycle to long fuel cycle. The owners have advanced further requirement about the length of cycle with 510 EFPD. Using KASKAD program package, the research on quick transition from year fuel cycle to long fuel cycle were carried out, and two long cycle fuel management cases were obtained. The important parameters of the two cases were analyzed, and all of the safety parameters meet the design requirements. The simple economic analysis of the equilibrium cycle was made also in this paper. The results of the research have engineering application value and can be applied in TNPS units 3 & 4 and VVER-1000, and can improve the economic efficiency of the plant.