In order to study the interaction between urea and mechanical structure, using direct shear test method, the shear modulus of urea was tested by C-LM4 computer measurement and control shear force measuring instrument. The obtained test curves show that: extrusion makes the binding strength between urea molecules reduce, shear force peak emerge, then decline rapidly; as rolling granules and surrounding granules formed compression and friction resistance in contact surface along the direction of shear, shear force emerges rise again. At the test temperature 22℃, ambient humidity 45%, the density of urea granules 1.33 × 103kg/m3, the values range of shear modulus of urea granules was measured, which was 0.23- 0.3GPa.