Donor-Acceptor (D-A) polymer field-effect transistors (pFETs) are at the cutting edge of organic electronics. However, some fundamental cognition of interface states remains unquantified, particularly at different dynamic scales. In this study, the interface states of D-A polymer transistors are quantified using the dynamic pumping method. The experimental results indicate that the interface state density of the transistor is insensitive to the measurement pulse condition and stays within the range of 10 12 ∼ 10 13 cm -2 . The experiments described in this paper provide a quantitative analysis of interface states. This analysis can serve as effective guidance for optimizing future devices.