A common-path two-window carrier interferometer is provided for applications of dynamic quantitative phase measurements.This interferometer is built on a 4f optical system with two apertures formed in the input plane,a ronchi grating is located between two lenses,and the spatial carrier is introduced by the defocus of the grating.T hen,a quantitative phase distribution of the specimen can be retrieved using the Fourier transform method.By giving the phase retrieval model of the interferometer and building an experimental set up,an evaporative water drop and a PMMA board under stress are recorded using this interferometer. The experimental results show that this interferometer not only has simple setup and good anti-i nterference performance,but also has good real-time ability,which makes it suitable for dyn amic quantitative phase measurements.