This paper summarized the clinical experience of professor HAN Mingxiang in diagnosing and treating fever of unknown origin （FUO） from the perspective of dampness， heat， constraint and deficiency. He holds that the core pathogenesis of FUO lies in dampness， heat， constraint and deficiency. Clinically， FUO can be differentiated into five syndromes including binding constraint of damp-heat， constraint fire lodging internally， residual pathogen retained in the lung， fever due to

qi

deficiency， and internal heat due to

yin

deficiency. Accordingly，

Longdan Xiegan Decoction and Shengjiang Powder

（龙胆泻肝汤合升降散） with modifications can be used to clear heat and drain dampness， soothe

qi

and blood， and

Shengjiang Powder and Danzhi Xiaoyao Powder

（升降散合丹栀逍遥散） with modifications can be used for diffusing and discharging constraint heat， regulating and unblocking

qi

mechanism.

Chaige Jieji Decoction

（柴葛解肌汤） with modifications is suggested to release the exterior and dissipate pathogen， clear and vent interal heat， and modified

Buzhong Yiqi Decoction

（补中益气汤） to replenish

qi

with sweet-warm medicinals and to raise

yang

and drain fire.

Yunv Decoction

（玉女煎） or

Zhibai Dihuang Pills

（知柏地黄丸） with modifications should be used for enriching

yin

and supplementing fire， clearing and removing deficiency and heat. Formulas are flexibly adjusted according to syndrome differentiation， with emphasis on harmonizing

zang

-

fu

（脏腑） function and balancing

qi

， blood，

yin

and

yang

， thereby providing a therapeutic approach for the clinical management of FUO.