Photoreflectance (PR) measurents have been performed on $In_xGa_{1-x}As/GaAs$ grown by molecular beam epitaxy (MBE). Bandgap $(E_0)$ of $In_xGa_{1-x}As$ epilayer measured from PR was separated as heavy-hole $(E_0(HH))$ and light-hole $(E_0(LH))$ by strain effect. The compositions and the strains of epilayer were obtained from the energy value of $E_0(HH)$ and from energy difference of $E_0(HH)$ and $E_0(LH)$, respectively. In addition, the PR signal of $E_0(LH)$ was diminished below 160 K. The interface electric field (E) of InGaAs/GaAs was increased from $0.75{ imes}10^5$ V/cm to $2.66{ imes}10^5$ V/cm as In composition increased, which was calculated from Franz-Keldysh oscillation (FKO) peaks. As the temperature dependence of the PR signal at x=0.09 sample, we obtained Varshni and Bose-Einstein coefficients.