In order to validate a procedure for creep rupture tests using small punch specimens, the influences of oxidation on the creep deflection curve, rupture time and ductility of miniature specimens were investigated. Using disc test specimens of 10mm in diameter and 0.5mm in thickness, a variety of small punch creep (SPC) tests for Cr5Mo steel at the condition of 550°C-404N and 650°C-189N under the protection of different Argon flow and in air atmosphere were firstly carried out. Metallographic observations, micro-hardness testing and measurement for these specimens of SPC test were performed. It indicates that the oxidized layer of specimens integrates and the residual thickness of specimens increases, while the hardness of specimens increases with the increment of the Argon flow. Moreover, the different oxidation degrees of specimens with the surface morphology were compared in this paper. The test results show the rupture time of specimens can be effectively prolonged by the protection of different Argon flow.