The invention discloses a corrosion judgment method for petrochemical equipment calculated based on water-phase state analysis. The corrosion judgment method comprises the following steps: 1) calculating water pressure in a device medium; 2) calculating saturated vapor pressure of water under the temperature/pressure set by an operation process; 3) determining device process nodes; 4) respectively analyzing the total water content among different process nodes; 5) analyzing different phase states of water and calculating content of water; 6) analyzing and judging medium flow states among the nodes; 7) analyzing the types and content of corrosive media among the nodes; 8) judging and analyzing different medium corrosion types and medium interactions; 9) combining the media with the flow states to analyze and judge the corrosion types and corrosion degrees. The corrosion judgment method for the petrochemical equipment calculated based on the water-phase state analysis disclosed by the invention has the advantages of not requiring manual field operation, analyzing an overall system, having high analysis precision and easy mastering and the like.