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Preliminary survey using refraction seismic method is an important thing to determine boundaries between weathered layer and rigid layer on highway geotechnical survey. The main thing in refraction seismic survey is to do interpretation survey result to accurate subsurface data. This research conducted subsurface velocity modeling using refraction seismic tomography. The purpose on this research is to make 2D velocity model to determine and analyze boundaries between weathered layer and rigid layer lithology for highway construction corresponding to ASTM D 5777 standard on each line from FRMLN field consist of line E2, E3, E4, and E5. Acquisition data using generalized-reciprocal method with several processing data stages consist of static correction, filtering, gain, first-break picking, inversion and tomography modeling. Based on modeling result, there is two kind of weathered layer lithology and three kind of rigid rocks lithology on research location. Weathered layer lithology consist of top soil in velocity 0-375 m/s and weathered layered (soil) in velocity 750-1125 m/s, while rigid rocks lithology consist of tuff in velocity 1500-1875 m/s, silicic tuff in velocity 2250-4125 m/s, and andesite in velocity more than 5250 m/s. Identified layer which occur a weathering in LINE E2 had a thickness variation around 2-6.3 meter, LINE E3 had a thickness variation around 1-5.6 meter, and LINE E5 had a thickness variation around 1-4 meter from surface.