Abstract: Soybean nodule formation and nitrogen-fixation are energy-consuming processes, which need a high demand of phosphorus nutrition. Low phosphorus stress could significantly affect the nodule initiation, development and nitrogen-fixation in soybean. bHLH transcription factor GmPTF1 has been demonstrated to improve the ability of tolerance for phosphorus starvation in soybean, while its role in nodule development and nitrogen-fixation remains unclear. In view of this, the GmPTF1 was cloned in soybean nodule, and its upstream promoter regulation elements was analyzed. And also, the gene expression and function in the process of nodule formation and nitrogen fixation under different phosphorus conditions were studied. The results showed that several nodule-specific expression elements were found in the promoter of GmPTF1, and a predominant expression of GmPTF1 was demonstrated in nodules via qRT-PCR. Moreover, the relative higher expression levels of GmPTF1 under low phosphorus condition were observed than that under normal phosphorus condition, which implied that GmPTF1 could respond to phosphorus deficiency and might play an important function in nodules. Further analysis showed that the over-expression of GmPTF1 in soybean complex plants significantly increased the nodule number（32.3%）, fresh weight（31.6%）, nitrogenase activity（32.2%） and phosphorus content（36.6%） under low phosphorus condition, while RNAi plants showed significant decrease on these related traits with nodule number（27.4%）, fresh weight（36.7%）, nitrogenase activity（24.3%） and phosphorus content（29.0%）, respectively. In addition, the significant higher expressions of related genes containing E-box（binding motif of transcription factor GmPTF1） were found in the over-expressed transgenic nodules, suggesting that the promotion of GmPTF1 for nodulation and nitrogen-fixation might due to the regulation of these E-box containing related genes in soybean. Thus, the function of transcription factor GmPTF1 for facilitating nodulation and nitrogen-fixation is dissected in this study, which provides gene resource for nitrogen-fixation genetic improvement in soybean.