Inclusion Criteria:

1. Written informed consent was submitted by subjects or their legal guardian
2. Bipolar disorder (296.0x, 296.4x) is diagnosed by the Structured Clinical Interview for DSM-IV Axis I Disorders - Patient Edition (SCID), based on the 4th edition of US Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)
3. Aged between 18 and 65, male and female, Han nationality
4. In the acute phase of mania episode and YMRS total score is at least 22 at baseline.
5. The following drugs (lithium carbonate, sodium valproate, risperidone or olanzapine) were received as previous maintain treatment( monotherapy or combination therapy) in adequate dose according to label within three months before this mania episode.
6. Child-bearing potential female patients should conduct urine pregnancy test (HCG) at the enrolment, and the result should be negative; and also willing to take contraception measures during the study period
7. Be able to understand and comply with the requirements of the study

Exclusion Criteria:

1. Women in pregnancy or lactation
2. The duration of this mania episode is at most 2 weeks at enrollment.
3. DSM-IV Axis I Disorders except bipolar disorder (296.0x, 296.4x)
4. Patients with symptoms of obvious suicide (MADRS No. 10 score ≥4), self-injured or harmful to others, as judged by the investigators
5. Known intolerance or lack of response to quetiapine fumarate, as judged by the investigators
6. Patients with non-compliance by his history as judged by the investigators
7. Use of any potent cytochrome P450 3A4 inhibitors in the 14 days preceding randomization, including but not limited as ketoconazole, itraconazole, fluconazole, erythromycin, clarithromycin, troleandomycin, indinavir, nelfinavir, ritonavir, fluvoxamine, and saquinavir
8. Use of potent cytochrome P450 inducers in the 14 days preceding randomization, including but not limited as phenytoin, carbamazepine, barbiturates, rifampin, St. John's Wort, and glucocorticoids
9. long-acting antipsychotic drug was injected within 1 injection interval (prolonged acting injection) before randomization
10. Use of clozapine in the 28 days preceding randomization
11. Substance or alcohol dependence according to the DSM-IV criteria at randomization (except complete recovered, and caffeine and nicotine dependence)
12. Dependence for the following drugs according to the DSM-IV standard at 4 weeks preceding randomization: opioids, amphetamine, barbiturates, cocaine, cannabis, or hallucinogens
13. Medical conditions that would affect absorption, distribution, metabolism or excretion of study treatment.
14. Clinical evidence for the relevant diseases (e.g. renal or hepatic dysfunction, severe coronary heart disease, cerebrovascular disease, hepatitis and acquired immunodeficiency syndrome (AIDS))
15. Unstable conditions (e.g. hypertension, congestive heart failure, unstable angina pectoris) or in the opinion of the investigator would be negatively affected by study medication or that would affect study medication, or has a medical history of chronic body disease.
16. Medical history with seizure disorder, except for febrile convulsion
17. Persons involved in the study design and conducting (suitable for the working staff in AstraZeneca and study site)
18. Participation in another clinical study within 4 weeks (or longer time according to the local requirement) of randomisation
19. Patients with diabetes mellitus (DM)
20. An absolute neutrophil count (ANC) of < 1.5 x 109/L
21. Thyroid-stimulating hormone level is more than 10% above the upper limit of the normal range, regardless of treatment for hypothyroidism or hyperthyroidism.
22. Abnormal ECG with clinical significance at enrollment indicating abnormal function in the heart, as judged by the investigator
23. Previous enrolment in the present study.