The invention relates to an apparatus for determining low expansion foam drainage. The apparatus comprises a foam receiver, a support, a foam receiving tank and a drainage receiving tank; the foam receiver comprises an upper receiving plate and a lower foam diverting nozzle, the upper receiving plate is a half conical curved slab, the upper port of the half conical curved slab is inwardly withdrawn, and the lower port and the foam diverting nozzle are connected integrally and smoothly; an opposite side of the half conical curved slab and an opening of the foam diverting nozzle are communicated, and the foam diverting nozzle is fixed on the support; the bottom part of the support is provided with a drainage measuring device support, the drainage receiving tank is fixed on the drainage measuring device support, the center of the top of the drainage receiving tank and a foam receiving tank are communicated through a drainage port, and the top of the foam receiving tank and the foam diverting nozzle are connected. The apparatus has the advantages of simple structure, reasonable design, low cost, test precision of foaming multiple and drainage time of the low expansion foam drainage is effectively improved, and the apparatus is worthy to promote and apply.