Abstract: The achievement of electrical spin control is highly desirable. One promising strategy involves electrically modulating the Rashba spin orbital coupling effect in materials. A semiconductor with high sensitivity in its Rashba constant to external electric fields holds great potential for short channel lengths in spin field-effect transistors, which is crucial for preserving spin coherence and enhancing integration density. Hence, two-dimensional (2D) Rashba semiconductors with large Rashba constants and significant electric field responses are highly desirable. Herein, by employing first-principles calculations, we design a thermodynamically stable 2D Rashba semiconductor, YSbTe₃, which possesses an indirect band gap of 1.04 eV, a large Rashba constant of 1.54 eV·Å and a strong electric field response of up to 4.80 e·Å². In particular, the Rashba constant dependence on the electric field shows an unusual nonlinear relationship. At the same time, YSbTe₃ has been identified as a 2D ferroelectric material with a moderate polarization switching energy barrier (~ 0.33 eV per formula). By changing the electric polarization direction, the Rashba spin texture of YSbTe₃ can be reversed. These outstanding properties make the ferroelectric Rashba semiconductor YSbTe₃ quite promising for spintronic applications.