Subdural hematoma in infants often occurs in the first few months of life and is characterized by rapid increase in head circumference, increased intracranial pressure, irritability, vomiting, altered muscle tone and seizures, and is a manifestation of delayed hemorrhage intracranial hemorrhage. The most important cause of intracranial hemorrhage in infants is late-onset vitamin K deficiency, with a higher incidence in male infants than in female infants. Late onset vitamin K (Vitk) deficiency is a Vitk deficiency that occurs after 2 weeks of life and is often combined with intracranial hemorrhage, with spontaneous intracranial hemorrhage or hematoma being the most common. The age of onset is 8 days to 12 months after birth, and more than 96% appear in infants less than 3 months of age. The rate of bleeding in low birth weight infants with vitamin K deficiency is five times higher than in normal birth weight infants, and minor trauma (e.g., a fall from a bed or couch) may lead to delayed acute subdural hemorrhage. The early clinical presentation of intracranial hemorrhage due to late-onset vitamin K deficiency is complex and atypical and can be easily misdiagnosed. Non-traumatic subdural hemorrhage is often first presented by imaging reports. Cranial ultrasonography does not easily detect subarachnoid hemorrhage and is less accurate for the diagnosis of subdural hematoma due to the limitation of scanning angle. In contrast, cranial MRI examination can directly observe the site of intracranial lesions and clarify the type and degree of hemorrhage; it can dynamically observe the lesions and estimate the prognosis of clinical treatment. In this group of 19 children, the vital signs were stable at the time of consultation, there was no bleeding from other parts, and the cranial ultrasound suggested external hydrocephalus. Later, the cranial MRI examination revealed a subdural hematoma, which showed two to three semilunar high-density shadows, and the hematoma was mainly in the parietal and temporal areas. Therefore, in infants with rapid clinical increase in head circumference, full fontanelle, irritability and vomiting, the presence of subdural hematoma should be noted even though there is no history of cranial trauma, and timely cranial imaging should be performed to prevent missed diagnosis. Intracranial hemorrhage is the most serious clinical manifestation of vitamin K deficiency and is an important cause of infant death and disability, with a death rate of 30.3% in seven provinces in China. There are also reports in the literature that the death rate is 30% to 50%, and about 50% of survivors have varying degrees of sequelae. The key to reducing the incidence of death and sequelae is to raise awareness of the disease and to improve the cure rate through early diagnosis and treatment. Since this disease is a spontaneous intracranial hemorrhage caused by vitamin K deficiency, vitamin K can be used to achieve the purpose of hemostasis, and the treatment of this disease with intracranial hematoma is mostly non-surgical in China.