V-based kagome materials AV₃Sb₅ (A = K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a ₀ × 2a ₀ CDW (charge density wave with in-plane 2 × 2 superlattice modulation) in AV₃Sb₅, an additional 1 × 4 (4a ₀) unidirectional stripe order has been observed at the Sb surface of RbV₃Sb₅ and CsV₃Sb₅. However, the stability and electronic nature of the 4a ₀ stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a ₀ stripe order on the Sb-terminated surface of CsV₃Sb₅. We find that the 4a ₀ stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a ₀ stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV₃Sb₅.