Aluminum and chromium were simultaneously co-deposited on the austenitic stainless steel substrates by pack cementation process. The effects of various combinations(masteralloy-activator-diffusion process) on the characteristics of coating layer on 310S and 316 were investigated. The most important factor controlling the simultaneous Cr-Al coating was composition of the masteralloy. The 80Cr-20Al(wt%) masteralloy exhibited better coating characteristics than the 95Cr-5Al(wt%) masteralloy. The 2-step coating cycle showed more desirable coating layer than the 1-step coating cycle. The coating morphology of each specimen consisted of two distinct layers, an outer layer of a brittle and continuous β-NiAl intermetallic phase and an underlying diffusion zone. In the same coating cycle with the same masteralloy composition, the more uniform coated layer was formed on 316 than on 310S due to the austenite stabilization of the substrate.