The evolution of Ni and V species during CO2/H2O/H2O + O-2 gasification is investigated at 600-1500 degrees C. The high S content inhibits the conversion of Ni3S2 into Ni and facilitates the formation of FeS, thus inhibiting the formation of FeV2O4 (s). During CO2 gasification, Ni exists in Ni3S2 and is converted into Ni at above 1200 degrees C. The V compound undergoes a mutual conversion between V2O3 and FeV2O4. Ni in Handan petroleum coke (petcoke) is converted into AlNi2O4 and FeNi2O4 during H2O gasification given the high contents of Fe and Al. The O-2 promotes the decomposition of spinel, thereby reserving the Fe in slag-phase FeS. The difference in the mineral transformation between samples increases with the oxidizability of the gasifying agent. Ni is the main cause of fouling in the CO2 atmosphere, while H2O can alleviate this condition; V is mainly involved in erosion. For industrial application, petcoke with lower V and S contents is highly recommended operation.