Exposure to phthalates has recently become a significant public health concern. We measured phthalate concentrations in dust and glass window films in 101 dormitories at 13 universities in Beijing of China from October to December, 2019. According to the measurement results, we analyzed phthalate characteristics, and examined possible phthalate sources using the positive matrix factorization (PMF) model. In addition, based on phthalate concentrations in dust and glass window films, we estimated the gas-phase phthalate concentrations using the equilibrium-partitioning model. The detection frequency of ten phthalates ranged from 79.2% to 100% in dust and from 84.2% to 100% in the window films, respectively. Di-n-butyl phthalate (DnBP), dicyclohexyl phthalate (DCHP) and di (2-ethylhexyl) phthalate (DEHP) are the most abundant phthalates in the two indoor media. PMF model is a modified factorization method that can quantify the contribution of sources to samples based on the composition or fingerprints of sources. In this study, The PMF results indicated that phthalates in dust and glass window film originate from three and four types of sources. The estimation results showed that the gas-phase concentrations of di-iso-butyl phthalate (DiBP), DnBP, di (2-methoxyethyl) phthalate (DMEP), di (2-ethoxyethyl) phthalate (DEEP), dipentyl phthalate (DPP) and dihexyl phthalate (DHP) are in an order of magnitude. The relative error of estimation for DCHP, DEHP, di-n-octyl phthalate (DnOP) and di-nonyl phthalate (DNP) is large, which may be due to their high Koa values (>11).