The quantum confined stark effect of InGaAs/InAlAs MQW heterostructures lattice-matched to InP substrate, grown by Chinese-built molecular beam epitaxy (MBE) system, is observed by absorption photocurrent spectra measurements, as well as the anisotropic elec-troabsorption of MQWs. The structure parameters of the epitaxied materials, which can be used to fabricate waveguide MQW electroabsorption modulators, were determined from double crystal X-ray diffraction measurements and computer simulations. The theoretical calculations of absorption-edge red shift compared with experimental results shows that the built-in-potential of the p-i-n junction can not be neglected.