Stress-strain relationships over the full range of strains of stainless steels are often needed as input in advanced numerical modeling for structural behavior. Although a number of stress-strain models have been developed for stainless steels; only two models by Rasmussen [1] and Quach et al. [2], respectively, can provide predictions for stainless steels over the full range of strains up to the ultimate strain by using only three basic Ramberg-Osgood parameters ( , and ). These two existing models were developed based on an interpretation of limited available experimental data from only virgin materials and flat materials of few alloys (i.e., austenitic, ferritic and duplex alloys). Thus, these two models may not be applicable to materials with a greater amount of cold work (such as corner materials) and are not applicable to other alloys such as lean duplex alloys and high strength austenitic alloys (H.S.A.) which become more popular in structural applications. This paper presents the refinements of these two models, which are able to provide accurate predictions for a wide range of stainless steel alloys with various levels of cold work. In the present study, a large amount of coupon test data reported in existing literatures have been collected and analyzed, and these tested coupons were cut from virgin sheets, flats and corners of cold-formed stainless steel sections with various shapes. The refined models have been developed by a careful interpretation of existing experimental data. The accuracy of the refined models has been demonstrated by comparing their predictions with test results.