Recently, the authors proposed a new metaheuristics method for continuous optimization problems based on analogy of spiral phenomena in nature which is called Spiral Optimization. The Spiral Optimization has two setting parameters: the convergence rate r and the rotation angle.. However, any adjustment methods or policies for them has not been studied so far. This paper especially focuses on the convergence rate r and develops its adjustment method through statistically analyzing its properties. The effectiveness is verified from simulation results under some conditions.