Abstract: The random responses of core barrel of a nuclear reactor excited by a fluctuating flow are discussed in this paper. Fluid dynamic forces are divided into two parts, free vibrating fluid dynamics and fluctuating fluid dynamics. By means of finite element method of structure, a theoretic method is developed to analyze the root of mean square of responses of a core barrel structure in turbulence. It is the focal point to analyze the effects of the mean velocity, the strength of turbulence and the integral measure of turbulence on the root of mean square of structure response.