Although anti-angiogenic (AA) therapy is widely used in clinical practice, it is often challenged by insufficient efficacy and intrinsic resistance. Some studies have reported that AA therapy can even increase tumor metastasis. However, whether this is due to a specific AA drug causing a specific tumor to metastasize or because the anti-angiogenic theory has some "inherent vice" that may inevitably lead to tumor dissemination remains a mystery. Herein, we designed a model that completely blocks tumor blood supply using a physical barrier to examine tumor behavior in such circumstances. Surprisingly, we found that cutting off the blood supply could neither eliminate the primary tumor cells nor prevent local invasion or formation of distant metastases. By using a mathematical method to simulate tumor behavior, we found that blocking tumor blood supply may lead to an inevitable consequence: the cells that can tolerate blood deficiency are "naturally selected" and survive, whereas a portion of cells are promoted to escape from the "starvation" area by the consistent environmental stress until they are spread throughout the body. This may be an intrinsic disadvantage of the AA strategy, which will inevitably cause the tumor, particularly highly metastatic tumors, to spread more aggressively.