Id proteins,or inhibitors of differentiation/DNA binding,are negative regulators of helix-loop-helix(HLH) type transcription factor,and they can inhibit cell differentiation and promote cell proliferation.Many experiments have proven that high expression of Id proteins in tumors was significantly related to malignant behaviors of tumors,such as tumor invasion and metastasis,suggesting Id proteins can be used to predict the prognosis of tumors.Abnormal expression of Id protein in malignant tumor might be associated with the invasive phenotype and poor prognosis of tumors.Id protein-targeted therapy can effectively inhibit tumor proliferation,invasion and metastasis.This paper reviews the mechanism by which Id protein influences the prognostic factors,such as malignant proliferation,invasion and metastasis,angiogenesis and the researches on progress of related clinical researches.