With the social and economic development of Lake Taihu Basin, polycyclic aromatic hydrocarbons (PAHs) have gradually accumulated in various environmental media, increasing severe pollution and posing severe threat to the ecological environment of Lake Taihu and the surrounding human health. To explore the source and ecological risk of PAHs in Lake Taihu sediments, 30 surface sediment samples were collected in Lake Taihu in the winter of 2021. The contents of 16 PAHs were detected by gas chromatography-mass spectrometry (GC-MS). The source analysis and ecological risk assessment were carried out using the receptor model and the benzo[a]pyrene (BaP) toxicity equivalent method. The contribution of each source was combined with the toxicity equivalent concentration to quantify the source risk. The results showed that the total content of 16 PAHs in the surface sediments of Lake Taihu had a range from 124-592 ng/g, with an average value of 294 ng/g and a median value of 279 ng/g. High molecular weight polycyclic aromatic hydrocarbons (HMW PAHs) were the main components, accounting for 67% of PAHs. The high concentration areas were Zhushan Bay, Meiliang Bay, Gonghu Bay and West Lake Taihu. The PAHs content of Lake Taihu sediments was low compared with other lake sediments in previous publications. The results of source analysis showed that PAHs in the surface sediment of Lake Taihu were mainly from traffic emissions (29.1%), coal combustion (26.7%), biomass combustion (28.7%), and petroleum (15.6%). The results of ecological risk assessment showed that the mean toxic equivalent concentrations (TEQ_BaP) of benzo[a]pyrene were 19.34 ng/g, 17.81 ng/g, 16.33 ng/g and 9.1 ng/g, respectively, which were less than 70ng/g (almost risk-free). Some areas of West Lake Taihu, Gonghu Bay and Meiliang Bay had a ΣTEQ_BaP greater than 70 ng/g, and had potential risk and toxicity. For pollution control in future, we should focus on pollutant loading into the northwest of Lake Taihu. This study can provide data support for studying PAHs pollution in sediments, and provide a theoretical basis for local governments to control PAHs pollution accurately and efficiently.