A rapid and resolutive reverse-phase high-performance liquid chromatography–electrospray ionization–quadrupoles–time of flight-mass spectrometry method was established for the screening and identification of the phenolic compounds in the 70% ethanolic extracts from the five parts (roots, stems, leaves, seeds, and exocarps) of Abutilon theophrasti Medic.. Separation and detection conditions were optimized by using a 22 mixing standard, which included phenolic acids, flavonoids and a naphthalene compound. Optimum LC separation was achieved on a C₁₈ analytical column (250 mm x 4.6 mm id, 5 μm) by gradient elution with water containing 0.1% v/v formic acid (pH 2.4) and acetonitrile as mobile phases, at a flow rate of 1.0 mL/min. The developed method was applied to the study on the constituents of A. theophrasti Medic., and 16 compounds were unequivocally identified with standards. Meanwhile, 37 constituents were tentatively identified by comparing with references. In addition, accurate molecular formulae were conjectured for unknown compounds. To our knowledge, little is known about how these compounds are distributed in A. theophrasti Medic.. Hence, it is clear that the comprehensive analysis of the phenolic compounds of A. theophrasti Medic. is helpful for the quality control and understanding the usage and function of the herb and its products.