With the development of small unmanned air vehicles, the urge for building the experimental facilities has emerged for the research on the low Reynolds number aerodynamics. In this paper, a five-component internal sting balance with the capacity of 10 N for forces and of 0.5 N·m for moments, which is to be installed in a close-circuit low Reynolds number wind tunnel for small unmanned air vehicle tests, was verified to investigate the interaction effect of its different components. Experimental setups and a sequence of evaluated procedures were designed to implement the application of different range of loads with pitch and roll angle coupled so as to investigate the interaction effect of different components by covering the full load range of sting balance. The sting balance was successfully verified with the designed experimental setups and procedures. Evaluation results showed that the interaction effect between balance components enhanced the measurement error and deteriorated the measurement precision. Moreover, it was also found that both precision and error depended on the loads. Relative error analysis revealed that the average relative error of all components was less than 2.1%. Hysteresis test showed that all balance component exhibited little hysteresis property except that side force component exhibited a mild hysteresis at lower load range.