The method of fracturing of oil gas reservoir is considered as an instrumental one for maximizing the yield. Multiple loads in a well fracturing operation may compel tubing string to yield, break and/buckle in a permanent spiral, leading to severe financial deficit. Mathematical models for mechanical analysis of fracturing string in whole fracturing operation are developed on the basis of operation procedures of well fracturing, with full consideration of well trajectory, component of fracturing string, borehole fluid property, internal and external pressure, friction factor between fracturing string and well wall, tubing temperature, packer types, piston effect of packer, helical buckling effect of tubing, slip joint, etc.. These mathematical models are solved with differential methods, obtaining parameters such as tension force, torque, stress, safety factor, stability, and elongation etc. Strength calibration of the string is formed. Software for mechanical analysis of tubing string in fracturing operation is developed with Visual Basic 2008. A case study of field application is also provided.