In recent years, cortisol had been used as a biomarker to assess stress in dogs. In order to evaluate the welfare of dogs,we reviewed the cortisol levels and changes in dogs under various stress and explored the influential factors which could relieve stress according to the variation law of cortisol levels ,so?as?to improve the measures to reduce stress in dogs. It is recommended to apply cortisol measurement and behavioral observation comprehensively to evaluate stress in dogs more accurately.