Interpass idle time is an important parameter affecting the thermal stress distribution in weld-based rapid prototyping. In this paper, the effects of interpass idle time on thermal stresses in multipass multilayer weld-based rapid prototyping are investigated using numerical simulation. Meanwhile the single-layer weld-based rapid prototyping experiment is carried out, and the residual stresses are measured in the blind-hole method. The variation trend of calculated residual stresses agrees with that of experimental measurements. The research results indicate that there exist stress release effects of rear pass on fore passes and that of rear layer on fore layers. The interpass and interlayer stresses and residual stresses are significantly dependent on interpass idle time. The residual stresses of deposition workpiece decrease with the increase of interpass idle time, whereas the interpass and interlayer stresses on the central line of substrate increase with the increase of interpass idle time.