Nitrogen and phosphorus are the key limiting factors of lake eutrophication. The study on the distribution characteristics and source analysis of nitrogen and phosphorus fractions in water and sediment can effectively reveal the process and mechanism of water eutrophication and analyze the pollution sources. As one of the most important water sources in the Xiongan New Area, the eutrophication of Baiyangdian Lake is serious, and the pollution of nitrogen and phosphorus is not optimistic. The study on the distribution characteristics and source analysis of nitrogen and phosphorus fractions is helpful to the analysis of nitrogen and phosphorus pollution in this area. However, there are few studies on the distribution of nitrogen and phosphorus fractions in sediment and water simultaneously, and the quantitative analysis of the contribution of nitrogen and phosphorus fractions by various pollution sources using models. In this study, the distribution characteristics of nitrogen and phosphorus in water and sediments of Baiyangdian Lake were studied by spectrophotometry. The contribution of different sources to nitrogen and phosphorus fractions was analyzed based on absolute principle components score combined with multivariate linear regression (APCS-MLR) model. The results showed that the content of total nitrogen (TN) (1.41~4.64 mg·L^-1) in the water of Baiyangdian Lake exceeded the environmental quality standards and were all heavy eutrophication; the total phosphorus (TP) content (0.043~0.273 mg·L^-1) in the water was also relatively seriously polluted, 95.8% of the sampling point were water quality of Class Ⅳ and above. The total proportion of ammonia nitrogen ($NH_{4}^{+}-N$) and nitrate nitrogen ($NO_{3}^{-}-N$) that could be directly absorbed and utilized by algae and plants reached 54.9%. In addition, the dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP), which contributed a great deal to the eutrophication of water accounted for 52.8%. The distribution regularity of nitrogen and phosphorus total amount and fractions showed that the eutrophication of Baiyangdian Lake was not optimistic, the pollution of Baiyangdian scenic area and margin area was relatively serious, and the proportion of nitrogen and phosphorus fractions which had great influence on water eutrophication was large. The ratio of bioavailable nitrogen (the sum of EN and HCl-N) to TN was 17.9%~66.4%, and the proportion of bioavailable phosphorus (BAP) in TP was 8.50%~28.0%. These results indicated a great risk of nitrogen and phosphorus release in the sediments of Baiyangdian Lake. The results of the principal component analysis showed that nitrogen and phosphorus pollution in Baiyangdian scenic area was more serious than that in other areas. The results of the APCS-MLR model showed that the contribution of domestic source pollution to nitrogen and phosphorus fractions were large, especially in sediments, agricultural pollution, animal and plant residues decomposition and aquaculture also contributed significantly to the content of different nitrogen and phosphorus fractions.