Aiming at the risk aversion of adverse selection and efficiency improvement in maintenance ally selection, an efficient and reliable Ally Selection System is proposed. The system employs agents to decompose complicated equipment maintenance tasks, and employs mobile agents and XML technique to convey order and capacity information between the center factory and the potential allies. Reliability evaluation is introduced to ensure the objective description of the potential allies' capacity information so as to guarantee the efficient search and accurate assessment of the potential allies. Finally, the capabilities of the proposed system are demonstrated in the equipment maintenance of a petrochemical company.