Most aircraft bolted joints consist of multiple bolts, and they may share the load unevenly due to the brittle nature of composites, which will easily lead to the premature failure of the joints. In order to decrease the bolt load inequality, the common method is to apply clearance fit at the most highly loaded bolt. However, it is always difficult to determine the clearance value. In this paper, a new method which is based on First Order Taylor Expansion was proposed to compute these values approximately. First, the First Order Taylor expansion was used to get the linear equation between the bolt load and the bolt-hole clearance. Then, under a given external load, using the bolt load when all the bolts share the load equally as the known parameters, and using the bolt-hole clearance as unknown parameters, a linear equation group is solved. The bolt-hole clearance was approximately calculated. The method was validated by applying it to a five-bolt joint. After optimization, the bolt load ratio of the most loaded bolt decreased from 45.1% to 23.0%. The maximum tensile stress and compressive stress of the joint decreased by about 26% and 39%, respectively. Finally, based on the validated model, the influence of parameters such as width, row spacing, number of bolts and external load was discussed. The model was highly efficient and for optimizing of an n-bolt joint, only n+1 finite element models were needed to obtain the desired clearance fit values. The model is of great significance for the optimization design of multi-bolt joints.