Abstract: In allusion to the prevenient defaule in tank bottom eathodie protection numerical simulation using deep-well anode, neglecting the inconsecutivencss of the calculation environmental medium, the distinctness of the restriction conditions in metal material polarized potential curve experiment resulted in potential cal- based on one typical current density distribution hypothesis, the soil and the bitumen-sand groundwork composed the calculation environmental medium, approximately calculating polarized potential of the deep-well anode base on the cathodic protection physical model. This paper compares the field testing data with numerical result, proves the reliability of numerical method, studies the critical diameter tank which single deep-well anode can absolutely and effectively protect (equal to 56 m), develops the estimating technique of technique.