We present single-pixel phase microscopy (SPPM) without 4f system, as a novel common-path quantitative phase imaging method, to acquire the amplitude and phase of any transmissive object. To get rid of the 4f system and make the experimental setup more compact and practical, SPPM adopts the phase-modulated detection mode. A single microscopy objective is employed for image magnification, and a collecting lens is used to circumvent the quadratic phase factor introduced by the objective. A phase-only liquid crystal on silicon is utilized to modulate the phase of object light to achieve Hadamard basis scan phase imaging and Fourier basis scan phase imaging with a single photomultiplier tube. We apply SPPM to observe several different types of objects, from simple artificial objects to complex biological specimens. The experimental results show that SPPM provides clear imaging, accurate phase, and spatial resolution up to 2.19 µm (a spatial frequency of 456 lp/mm). Without the 4f system, SPPM can be implemented as an add-on module to existing optical microscopy, which facilitates its adoption in biomedical science and optical metrology.