[ $InxGa_{1-x}P/GaAs$ ] structures were grown by chemical beam epitaxy(CBE), Pure phosphine($PH_3$) gases were used as group V sources. for the group III sources, TEGa, TmIn were used. $InxGa_{1-x}P$ epilayer was grown on SI-GaAs substrate and has a 1-${mu}m$ thick. We have investigated the characteristics of $InxGa_{1-x}P$ by the photoreflectance(PR) spectroscopy, The PR spectrum of $InxGa_{1-x}P$ shows third-derivative feature whose Peaks Provide energy gap. The energy gap of $InxGa_{1-x}P$ has deduced composition x. From temperature dependance of PR spectra, temperature coefficient is $dEg/dT=-3.773{ imes}10^{-4}$ eV/K, and Varshni coefficients $alpha$ and $eta$ values obtained $4{ imes}10^4$ eV/K and 267 K respectively. Also, interaction $alpha$B was 19.4 meV using the Bose-Einstein temperature relation, and $Theta$ value related the average phonon frequency were 101.4 K. In particular, shoulder peak related to defects observed in PR signal that measured in temperature 82 K.