Anisotropic　2D　materials　exhibit　unique　optical,　electrical,　and　thermoelectric　properties　that　open　up　possibilities　for　diverse　angle-dependent　devices.　However,　the　explored　anisotropic　2D　materials　are　very　limited　and　the　methods　to　identify　the　crystal　orientations　and　to　study　the　in-plane　anisotropy　are　in　the　initial　stage.　Here　azimuth-dependent　reflectance　difference　microscopy　(ADRDM),　angle-resolved　Raman　spectra,　and　electrical　transport　measurements　are　used　to　systematically　characterize　the　influence　of　the　anisotropic　structure　on　in-plane　optical　and　electrical　anisotropy　of　2D　GeAs,　a　novel　group　IV-V　semiconductor.　It　is　proved　that　ADRDM　offers　a　way　to　quickly　identify　the　crystal　orientations　and　also　to　directly　characterize　the　in-plane　optical　anisotropy　of　layered　GeAs.　The　anisotropic　electrical　transport　behavior　of　few-layer　GeAs　field-effect　transistors　is　further　measured　and　the　anisotropic　ratio　of　the　mobility　is　as　high　as　4.6,　which　is　higher　than　the　other　2D　anisotropic　materials　such　as　black　phosphorus.　The　dependence　of　the　Raman　intensity　anisotropy　on　the　sample　thickness,　excitation　wavelength,　and　polarization　configuration　is　investigated　both　experimentally　and　theoretically.　These　data　will　be　useful　for　designing　new　high-performance　devices　and　the　results　suggest　a　general　methodology　for　characterizing　the　in-plane　anisotropy　of　low-symmetry　2D　materials.