The invention discloses an application of PCYOX1 (Prenylcysteine oxidase 1) protein as a biomarker of ischemic cerebral stroke, and particularly discloses the application of the PCYOX1 protein, an active fragment of the PCYOX1 protein or a substance for detecting the PCYOX1 protein or the active fragment of the PCYOX1 protein in a product for diagnosing ischemic cerebral stroke and/or evaluating the risk of suffering from ischemic cerebral stroke. The PCYOX1 protein related with cerebral stroke is provided, and down-regulated expression of the PCYOX1 protein or the active fragment of the PCYOX1 protein in the cerebral stroke tissue is further proved. With the adoption of the protein for detecting cerebral stroke, not only can early detection be realized rapidly and effectively, but also therapeutic targets and important basis are provided for clinical applications such as gene therapy, drug therapy and the like.