Objective To investigate the basic biological functions of NKX3.1 with construction of a series of eukaryotic expression vector of NKX3.1 to study its effects on cell cycle and apoptosis.Methods The full-length reading frames (ORF) of NKX3.1 was amplified from normal human prostate tissue with polymerase chain reaction (PCR),the ORF was cloned into T vector,and then NKX3.1 was cloned into eukaryotic expression vector pcDNA3.1 (+) and pcDNA3.1 (-) with this T vector as template.NKX3.1 in pEGFP C1 was transfected into PC3 cell line,and C1 pEFP was taken as control to observe the localization of NKX3.1 in cells.At the same time,NKX3.1 in pcDNA3.1 and pcDNA3.1 were transfected into PC3 cells and the cells were collected after 24 ～48 hours to detect cell cycle and apoptosis by flow cytometry.Results The eukaryotic expression vector of NKX3.1 was constructed successfully.Fluorescent protein was ocated in the nucleus after transfection of NKX3.1 in pEGFP C1,but pEGP C1 was both expressed in nucleus and cytoplasm.There was significant effect on the early apoptosis (P＜0.01),but no effect on the cell cycle (P ＞ 0.05) after transfection of NKX3.1 compared to PC3 cell-transfected with empty vector of pcDNA3.1.Conclusions The result data suggest that NKX3.1 be nuclear protein and have effect on the early apoptosis of PC3 cell line based on the construction of eukaryotic expression vector.