The occurrence and distribution of phthalate acid esters (PAEs) in surface water of the Weihe River basin (eight mainstream sampling points and 15 tributary sampling points) in the Shaanxi section were investigated during the dry season, level period (spring), wet season and level period (autumn). The PAEs tested for were diethyl phthalate (DEP), di-n-butyl phthalate (DBP), dicyclohexyl phthalate (DCHP) and di-(2-ethylhexyl) phthalate (DEHP). The testing proceeded by millipore filtration, then solid phase extraction and then gas chromatography-mass spectrometry determination for all examined PAEs. The monitoring results indicated that, in terms of seasonal changes, concentration of the PAEs in the mainstream is: Dry season > Level period (spring) > Wet season ≈ Level period (autumn). An environmental risk assessment was then performed on PAE pollution levels of the Weihe River basin. This paper employed a risk assessment methodology to evaluate the potential adverse health effects of the individual PAE compounds according to their carcinogenicities. For DEP, DBP and DEHP, a low Risk Index (all of them were lower than the specified level of 1.0) reveals that small non-carcinogenic risks exist resulting from the presence of trace concentrations in the surface water of the Weihe River basin.