Abstract: In order to reduce the nut-losing rate and damaging rate in the process of peanut digging harvest, nut picking and shelling, especially in the process of peanut combine, the authors carried out experiments and analyzed the results on the mechanical properties of tensile and shear stress of the peanut stem, stem root node, nut root node and husk union, respecively, which used CTM-4503 type universal material testing machines and relevant testing equipments. The peanut for testing was obtained in nearly one month interval of peanut harvest time. Through the tests, the authors analyzed the maximun allowable tensile resistance and allowable shearing stress of peanut stem, stem root node, nut root node and husk union place. Through the mechanical analyse, the best harvesting time of peanut was determined. Taking Luhua No.14 peanut as an example, the best harvesting time was (122±1) days after sowing. The maximum allowable clamping force (49.71 N) and the maximum allowable tensile force (70.84 N) were given in the process of peanut combined clamping harvest at present and the tests showed that rupture of stem root node in peanut harvest was the main part of mechanical loss with the percentage of 95.7%. According to the operation quality index in operating quality industry standard for peanut harvesters given by Chinese Ministry of Agriculture, the maximum tensile force, 9.51 N, was given. Through the shear tests of the husk union place, the maximum shearing stress of the husk union place in different period was given. All those provide reference for equipment design and development of peanut harvester, nut picking and shelling, especially for that of combine harvester devices.