Gasification is a promising technology to dispose antibiotic mycelial dreg (AMD) which is a typical pharmaceutical hazardous bio-waste. However, the gasification of AMD is rarely studied. Since char gasification is the key step in the gasification process, the present work focused on the steam gasification of char. The influence of inorganic elements inside AMD char (mainly P, K and Ca) on the char gasification reactivity is investigated. Particularly, the effect of P on char gasification reactivity was deeply studied, and the co-effect of P, K and Ca on char gasification reactivity was firstly studied and explained. The obtained results suggested that P can deactivate the catalytic function of K and Ca on char gasification by forming K-phosphates and Ca-phosphates. The existence form of P can affect its inhibitory effect on K and Ca, and the pyrophosphate P had a stronger inhibiting effect than orthophosphate P. The deactivation of P on K is related to the ratio of K to P, and the bigger the ratio of K to P the less the deactivation of P on K. The existence of Ca can effectively eliminate the deactivation of P on K by reacting with P to form more stable Ca3(PO4)2.