Phosphatidyl ethanolamine-binding protein (PEBP) widely exist in plants and play important roles in regulating flowering, seed dormancy and the formation of underground storage organs (e.g. potato tubers and onion bulbs). However, up to now, there is few studies conducted on PEBP genes in sweet potato (Ipomoea batatas), and there is also no research published to reveal the key members of PEBP gene family that regulate the development of storage root of sweet potato. Our study first identified the number and types of the PEBP gene family in sweet potato through bioinformatics analysis. Then, to screen the candidate members of the PEBP gene family that regulate the development of storage root of sweet potato, the tissue specificity of PEBP gene expression and the dynamic changes of PEBP gene expression level in storage roots at different development stages were analyzed. To explore possible regulatory mechanism, the correlation between PEBP gene expression level and SWEET gene expression level in storage roots were also examined. The results are as follows: (1) A total of 15 putative PEBP genes were identified from the sweet potato genome, which were classified into 4 subfamilies: 5 of FT-like genes (IbFT1-5), 6 of TFL1-like genes (IbTFL1-6), 2 of MFT-like genes (IbMFT1-2), and 2 of PEBP-like genes (IbPEBP1-2). (2) Clustering analysis revealed that IbFT5 may promote the development of storage root of sweet potato, while IbTFL3 may inhibit the development. (3) The tissue specificity analysis of sweet potato PEBP gene expression showed that IbFT5, IbTFL4 and IbTFL6 not only showed higher expression levels in the diverse root tissues than in other tissues, but also had higher expression levels in roots than other PEBP genes. Therefore, it is speculated that the three PEBP genes may promote root enlargement. (4) The expression levels of the four candidate PEBP genes (IbFT5, IbTFL3, IbTFL4 and IbTFL6) obtained from the above two methods were determined in storage roots at different developmental stages (30, 60, 90 and 120 days after planting). It was found that the expression levels of IbFT5, IbTFL4 and IbTFL6 significantly increased with the development of root tubers, especially during the rapid expansion period (60-90 days), while the expression level of IbTFL3 rapidly de-creased during the rapid expansion period (60-90 days). Therefore, all the above measurement results indicate that IbFT5, IbTFL4 and IbTFL6 may promote root development, while IbTFL3 may inhibit root development. (5) With the increase of expression levels of IbFT5, IbTFL4 and IbTFL6, the expression levels of four out of the five highly ex-pressed SWEET genes (IbSWEET4, IbSWEET11, IbSWEET16 and IbSWEET19) in storage roots showed a continuous decreasing trend. This result is similar to the findings in potatoes, indicating that the PEBP gene of sweet potato may also inhibit SWEET activity and thus promotes the transportation of sugar to the storage roots through more efficient symplasmic pathway, which ultimately promotes the development of storage roots. In conclusion, this study not only determined the number and types of members of the PEBP gene family in the sweet potato genome, but also systematically identified four candidate PEBP genes affecting the development of sweet potato storage roots, which can provide a theoretical basis for further improvement of sweet potato yield in China.