A new semiconductor III-V five-element alloy AlGaInPAs had been grown successfully by liquid phase epitaxy (LPE). All our samples had mirror-like, flat, surfaces, X-ray double crystal diffraction, PL spectra and Hall measurements show that all our AlGaInPAs/GaAs samples had goad quality. The lattice-mismatch between AlGaInPAs epitaxial layer and GaAs substrate was better than 10(-3), FWHM values of PL peaks of our our samples were about 50 meV and the epitaxial layers were n type. The carrier concentration was about 4.4 x 10(15) cm(-3) and the mobility, about 900 cm(2)/Vs. The variation of composition along the direction of growth was also very small.