A study of the effect of Kerr's effect on fiber optic SMS as a strain sensor has been carried out in a simulation. The addition of the Kerr effect to the SMS fiber optic strain sensor is carried out by providing a high intensity and doping material with a nonlinear index on the multimode fiber optic. The Kerr effect given with variations power on the fiber optic strain sensor affects the refractive index of the fiber optic that increased. It can be observed on the wavelength spectrum graph, which shifts to a smaller wavelength when the change in the refractive index value is more significant and affects the sensor sensitivity. From the analysis of static characteristics, the highest sensitivity of the SMS fiber optic strain sensor was obtained by a 6 cm multimode fiber optic of 0.001844 dBm / μϵ. At the same time the highest sensitivity of the strain sensor with the Kerr effect was obtained by multimode 6 cm with doping CaF2 at an intensity of 1017 W/m², which was 0.008867 dBm / μϵ.