The effects of two types of silanes, which were bis (triethoxysilylpropyl) tetrasulfide (Te) and octyltriethoxysilane (Oc), on the extrusion properties of styrene-butadiene rubber (SBR) /silica (Si) composite were investigated from the viewpoint of the bound rubber. The surface roughness of the SBR extrudate slightly increased when adding Te, and didn't increase when adding Oc. On the other hand, the extrudate surface for SBR/Si composites was smooth, and it hardly changed with the addition of Te and Oc. It was shown that the addition of Te contributed to an increase of the swell ratio (SR) of SBR and SBR/Si. The SR of SBR was hardly changed with the addition of Oc, while the SR of SBR/Si slightly increased with the addition of Oc. Gel permeation chromatography showed that the molecular weight of SBR increased with the addition of Te, but that it did not vary with the addition of Oc. The bound rubber formed in the SBR/Si composites was reduced when adding Oc, but did not vary when adding Te. For each SBR/Si/silane composite, the SR was decreased when increasing the bound rubber. Therefore, it can be concluded that the SR of SBR／Si increased due to an increase in the molecular weight of SBR due to addition of Te, whereas the SR of SBR／Si increased due to a reduction of bound rubber when adding Oc.