We study the fractal rhythm in the ionization of Rydberg helium and lithium atoms in an electric field by using the semiclassical method.The fractal structures present a nested relationship layer by layer in the initial launch angles of the ionized electrons versus the escape time,which is defined as the rhythm attractor,and exhibit similar rhythm endings.The gradually enhanced chaotic regions of the escape time plots tend to broaden as the scaled energy increases.In addition,the fractal rhythm changes synchronously with the oscillations of the kinetic energy spectrum.We note that the intrinsic quality of the fractal rhythm is closely related to the kinetic energy distribution,that is,the inherent dynamic properties of the Hamiltonian equations have an impact on the fractal regularities.In addition,different ionizing closed trajectories exhibit iterate properties and the inherent beauty of symmetry.Our results and analysis can not only reveal new laws in the ionization of Rydberg atoms,but also promote the establishment of the dynamic mechanism of fractals.