The tensile deformation behavior, surface morphology, fracture mode and fracture morphology of SRR99 superalloy bicrystals were systematically investigated at room temperature in air. It is shown that the bicrystal with misorientation of 4° has little influence on the tensile properties, however the effect of grain boundary (GB) becomes obvious when the misorientation is 10°, for the bicrystals with misorientations of 16° and 18° the effect of GBs becomes much more serious. It is experimently found that slip is the most important deformation mode in the SRR99 superalloy bicrystals at room temperature. For the bicrystal with misorientation of 4°, slip bands would transfer through GB easily, and finally the specimens fractured along slip bands with typical slip characteristic on their fractography. In the bicrystal with misorientation of 10°,cracks nucleated and propagated either along slip bands or along GBs due to the impingement of slip bands and the strain accumulations, and finally the fracture instability happened along slip bands. The fracture morphology showed not only slip characteristic, but also the features of interdendritic cracks. In the bicrystals with misorientations of 16° and 18°, cracks initiated after yielding, and then propagated along GBs and the fracture surfaces mainly consisted of interdendritic cracks.