Given　the　time-domain　measurement　of　picoseconds　pulses　and　frequency-domain　measurement　of　high-frequency　modulation　have　limitations　to　realize,　this　paper　introduces　the　experiment　research　which　use　square-wave　modulation　laser　source　as　incident　light　source　of　the　diffusion　optical　tomography　in　homogeneous　medium.　Based　on　the　finite-element　method,　the　forward　model　can　be　established.　The　analytical　solution　of　the　homogeneous　medium　can　obtained　from　the　derivation　of　the　diffusion　equation,　after　that,　we　build　the　optical　experiment　platform,　derive　the　experimental　solution　from　the　platform.　Finally,　the　consistent　result　is　obtained　by　the　comparison　of　the　simulation,　the　analytical　solution　and　the　experimental　solution.　The　result　clearly　demonstrated　the　accuracy　and　effectiveness　of　the　proposed　method　which　use　square-wave　modulation　laser　source　as　incident　light　source　to　measure　the　light　intensity.