By combining the basic device equations of MOSFET with the polarization retention characteristics of ferroelectric thin films, a misfit strain and temperature-dependent retention model for ferroelectric-gate field-effect transistor (FeFET) is developed.This model gives the retention characteristics of ferroelectric films and FeFET memory device both in short and long time scales.Simulations demonstrate that the compressive strain improves and tensile strain degrades the retention time.Meanwhile, the temperature dependence of retention properties of FeFET has been investigated.It is expected that this work may offer some useful guidelines to improve the retention properties of FeFET using strain engineering.