Glucocorticoids (glucocorticoids, GC) are a kind of steroid hormones secreted by the fasciculate zona in the adrenal cortex, whose main component is cortisol. As glucocorticoids have strong effects of anti-inflammation, immunosuppression, anti-shock, anti-allergy, and anti-toxin, they are now widely used in clinical practice. However, due to their long term use in higher doses and the fact that their therapeutic doses and side effects-causing doses are close to each other, glucocorticoids often bring many side effects to the patients, including Cushing syndrome, severe infections, osteoporosis, skeletal muscle atrophy and necrosis, peptic ulcer, diabetes mellitus, acne, purple striae, and change in behavior and cognition. So it is necessary for us to fully understand the side effects of glucocorticoids and to know their application principles and methods in clinical practice.