Invasive fungal disease (IFD) refers to an infectious disease caused by fungi invading the human body, growing and reproducing in tissues, organs, or blood, and leading to inflammatory responses and tissue damage. Due to the suppression of immune system function during the disease and its treatment process, patients with hematological malignancies are prone to opportunistic infections, including IFD, with the lungs being the most common site of infection. In patients with hematological malignancies, IFD is often difficult to diagnose and progresses rapidly. Some patients become critically ill, which severely affects their prognosis. With the rapid development of molecular biology techniques, metagenomic next-generation sequencing (mNGS) of pathogenic microorganisms-as a broad-coverage, highly sensitive diagnostic tool with a short reporting cycle-has been widely applied in the etiological diagnosis of clinical infectious diseases. However, its clinical value in the diagnosis of IFD remains to be explored. This study is a single-center, single-arm, open-label clinical study to to explore the clinical performance of peripheral blood mNGS in the diagnosis and treatment of IFD in patients with hematological malignancies.