Abstract: In Chinese traditional timber structures，the way of stitching is often found in beam and purlin members． For 3-purlin beam and 5-purlin beam members，when their bearing capacity and rigidity are not adequate，they are often strengthened by the ways of stitching of beam-jiaobei or beam-suiliangfang． For purlin members，they are often strengthened by the way of stitching of purlin-suilinfang． The stitching beams are mainly two types which are small top and big bottom type and big top and small bottom type． In order to study the bending behavior including the failure mode and bending bearing capacity and strain distribution at mid-span section of timber stitching beams with small top and big bottom，the bending test on six specimens with traditional conformation were carried out，including three deal specimens and three fir specimens． The results show that the failure modes of this kind of stitching beams are all the brittle breakings of bottoms at lower beams． The distribution of section strain along the height of timber stitching beam basically obeys plane hypothesis． Based on the theoretical analysis and experimental results，the computing formulas of bending bearing capacity of this kind of timber stitching beams made of deal and fir were presented．