The investigators are undertaking a multicentre, randomised controlled trial of 120 adults with newly diagnosed ITP from 5 medical centers in China. Part of the participants are randomly selected to receive caffeic acid tablets combining dexamethasone and the other part are selected to receive high-dose dexamethasone treatment. Platelet count, bleeding and other symptoms were evaluated before and after treatment. Adverse events are also recorded throughout the study.

All participants' platelet count will be monitored weekly. Response will be evaluated after 3, 6 and 12 months after treatment. If the participant did not get complete response or response after 3 months, he would quit the trail.

Inclusion Criteria:

1. Meet the diagnostic criteria for immune thrombocytopenia
2. Untreated hospitalized patients, may be male or female, between the ages of 18 ~ 80 years
3. To show a platelet count <30 * 10^9/L, and with bleeding manifestations
4. Willing and able to sign written informed consent

Exclusion Criteria:

1. Received chemotherapy or anticoagulants or other drugs affecting the platelet counts within 3 months before the screening visit
2. Received second-line ITP-specific treatments (eg, cyclophosphamide, 6-mercaptopurine, vincristine, vinblastine, etc) within 3 months before the screening visit
3. Received high-dose steroids or IVIG in the 3 weeks prior to the start of the study
4. Current HIV infection or hepatitis B virus or hepatitis C virus infections
5. Severe medical condition (lung, hepatic or renal disorder) other than chronic ITP. Unstable or uncontrolled disease or condition related to or impacting cardiac function (e.g., unstable angina, congestive heart failure, uncontrolled hypertension or cardiac arrhythmia)
6. Female patients who are nursing or pregnant, who may be pregnant, or who contemplate pregnancy during the study period
7. Have a known diagnosis of other autoimmune diseases, established in the medical history and laboratory findings with positive results for the determination of antinuclear antibodies, anti-cardiolipin antibodies, lupus anticoagulant or direct Coombs test
8. Patients who are deemed unsuitable for the study by the investigator