This is a multicenter, open label, 4-week study. Study subjects are defined in Chinese Han nationality patients with acute mania of bipolar disorder (inpatients or outpatients). The screening phase is up to 7 days. The eligible patients in the screening phase can be enrolled into the treatment phase, the target dose is 400-800mg/day, and treatment period will last for 4 weeks. The objective is to evaluate the efficacy of quetiapine fumarate switching from other drugs used as monotherapy in the treatment of acute mania with bipolar disorder, and the relationship between the serum BDNF and quetiapine fumarate.