For　solving　the　defect　of　insufficient　structural　stiffness　in　soft　manipulator,　a　module　of　pneumatic　soft　manipulator　is　designed　according　to　the　characteristics　of　currently　soft　manipulator.　The　module　is　designed　by　variable　stiffness　principle　of　coupling　and　consist　of　two　connecting　plates　at　the　upper　and　lower　ends,　bending　chambers　between　in　the　two　plates　and　variable　stiffness　chamber　in　the　middle.　It　can　realize　modularity,　stiffness　adjustment　and　load　capacity　in　this　continuum　soft　manipulator.　Based　on　the　hyperelastic　material　characteristics　of　silicone,　a　non-linear　mechanical　model　suitable　for　pneumatic　soft　manipulator　is　established　for　analyzing　the　variable　stiffness.　Combining　with　the　torques　of　the　chambers　and　actual　bending　process　of　the　module,　this　paper　designed　a　static　tensile　test　for　evaluating　the　performance　of　variable　stiffness　chamber　by　applying　redundant　driving　moment.　Through　the　experiment　and　demonstration,　the　mapping　relation　between　the　inflatable　pressure　and　the　stiffness　of　the　module　is　obtained,　which　provides　the　mechanical　theory　support　for　the　stiffness　calculation　of　the　pneumatic　soft　manipulator　and　the　practical　application　of　the　module.　©　2020　Journal　of　Mechanical　Engineering.