The invention discloses a CMOS instrument amplifier based on current feedback. The CMOS instrument amplifier comprises a PMOS tube M1, a PMOS tube tube M6, a first current mirror, a second current mirror, an NMOS tube M2, an NMOS tube M3, an NMOS tube M4, an NMOS tube M5, a capacitor Cc1, a capacitor Cc2, a resistor R1, a resistor R2, a current source I1, a current source I2, a current source I3, a current source I4, a current source IC1 and a current source IC2; and the first current mirror comprises a PMOS tube M7 and a PMOS tube M8, and the second current mirror comprises a PMOS tube M9 and a PMOS tube M10. By adoption of the CMOS instrument amplifier disclosed by the invention, no input coupling capacitor is used, thereby eliminating the influence caused by the mismatch of the input coupling capacitor and improving the common mode rejection ratio of the amplifier; as a fully differential structure is adopted, the common mode rejection ratio is further improved; and the circuit branches are few, thereby realizing low power consumption.