The second-order photon correlation is fundamental and crucial for characterizing quantum statistical properties of optical fields. In this paper, the photon correlation characteristics of fluorescence emitted by cold atoms coupled with nanofiber waveguide modes are investigated and analyzed, and the impact of the number of atoms on the second-order photon correlation of the radiated fluorescence coupled into the nanofiber is experimentally explored in a cold atomic system. The results of the second-order photon correlation for the fluorescence collected from single-ended and dual-ended nanofiber show that, with the adjustment of the number of atoms in the cold atomic system, the single-ended second-order photon correlation transits from bunching to anti-bunching, while the dual-ended second-order photon correlation consistently maintains anti-bunching features. This research reveals the high-order photon correlation properties of the radiated optical field resulting from the interaction between cold atoms and nanofiber, and provides an experimental basis for the development of a cold-atom all-fiber quantum information platform.