Abstract: Aiming at the quite uneven load distributions in the multiple bolts and premature failure at the most highly loaded induced by the brittle nature of composites, the clearance between the bolt and its corresponding hole was adjusted to improve the unequal load distribution. Firstly, bolt-hole clearances was chosen as the design variable and a quadratic programming optimization model of load distribution for multi-bolt joint based upon spring-mass model was built. Then, the optimization model was solved by using interior point method and the global optimum solution of the optimization model was obtained. At last, as an example, the bolt-hole clearances of composite mechanical joint with 5 bolts were optimized. The calculation results obtained were compared with the prediction results from finite element model. It shows that model optimization results agree well with finite element results. After optimization, the maximum bolt load proportion decrease dramatically from 41.1% to 20%. The model can be used effectively and accurately in uniform design of load distributions for multi-bolt composite joints.