Abstract: Irregular columnar jointed basalt is widely distributed in Baihetan Hydropower Station,and it is the premise of engineering stability analysis to describe its geometric characteristics and study the scale of representative units. In this paper,a modeling method for columnar jointed rock mass is proposed,which considers the geometric characteristics of the polygonal side length and number of sides of the cylinder end face. This method mainly dynamically updates the Voronoi polygons by constantly perturbing the position of polygon center points in the Voronoi graph,combined with the short-edge elimination algorithm,until the maximum diagonal length regularity of polygons and the hexagon index is consistent with the field statistical results. Accurate simulation of geometric characteristics of end faces of columnar jointed rock masses could be achieved. The end faces of columnar jointed rock mass of Baihetan hydropower station are dominated by tetragons and pentagons,and the side lengths are mainly distributed between 7 and 30 cm,which is approximately normal distribution,with a regularity of about 0.85 and a hexagonal index of about 1.422. Using the modelling method proposed in this paper,the columnar jointed rock mass models of different sizes of Baihetan hydropower station are established. The regularity and hexagonal index in the model are consistent with the field statistical results. Through the uniaxial compression test numerical simulation of different sizes models of columnar jointed rock mass,the representative size of elastic modulus is obtained as 3 m×3 m. Finally,the influence of regularity on the elastic modulus of columnar jointed rock mass is analyzed. With the increase of regularity,the discreteness of elastic modulus of columnar jointed rock mass is weakened,and the average value gradually increases. The more regular the columnar jointed rock mass is,the weaker the anisotropy and the stronger the engineering stability.