PM_2.5 samples were collected from residential, commercial, plaza and public green spaces in Lin’an, Hangzhou, in spring (March and April) and winter (February and December) in 2017. PAHs were detected by gas chromatography-mass spectrometry (GC-MS), and their sources were identified using the diagnostic ratio (DR) and principal component analysis-multiple linear regression (PCA-MLR). The average PAH concentration in winter was 1.3 times that in spring (p < 0.01). The PAH concentrations in the green spaces decreased as commercial > residential > plaza > public green space (p < 0.05). The sources of PAHs were vehicle emissions and coal combustion pollution transported by northern Chinese air masses. Slightly higher excessive cancer risks were determined in the commercial and residential green spaces than in the plaza and public green spaces. Green coverage, pedestrian volume, traffic flow and building density greatly influenced the decrease in the PAH concentration in the green spaces. Among the 4 types of green spaces, public green space had the most ecological benefits and should be fully utilized in urban green space planning to improve public health in urban spaces.