We investigate Rydberg $|65D_{5/2}\rangle $ $\to$ $|66P_{3/2}\rangle$ superradiance in a dense ultracold cesium atoms, where the ground atoms are excited to $|65D_{5/2}\rangle$ Rydberg states via two-photon excitation in a standard magneto-optical trap. The superradiant spectrum of $|65D_{5/2}\rangle$ $\to$ $|66P_{3/2}\rangle$ is obtained using the state selective field ionization technique. We observe its dynamic evolution process by varying the delay time of ionization field $t_{d}$. The results show that the evolution process of $|65D_{5/2}\rangle $ $\to$ $|66P_{3/2}\rangle$ is much shorter than its radiation lifetime at room temperature, which verify the superradiance effect. The dependence of superradiance process on Rydberg atoms number $N_{e}$ and principal quantum number $n$ are investigated. The results shows the superradiance become fast with increasing $N_{e}$, while it is suppressed for stronger van der Waals (vdW) interaction. Superradiance has a potential application in quantum technologies, and the Rydberg atom is an ideal medium for superradiance. Our system is good for studying the strong two-body interaction between Rydberg atoms.