Abstract: The utilizing parameters of small tractors in Gansu Provinces, such as the available power, remain， fuel consumption rate and the maintenance cost are surveyed and statistically analyzed for several years. The regression formula was established and the lifespan cost of the small tractors can be obtained with this formula. The average cost of different lifespan of the small tractors were calculated step by step of years, and a conclusion of that the economical usage lifespan is about 6 years was given. In practice, the renew period of the small tractors were varying about the economical lifespan.