Abstract: The transient temperature characteristics of high power laser diode(LD) with multiple emitters were presented and discussed in this paper. The transient temperature response curves were measured by electrical temperature sensitive parameter method. Structure function method was performed to evaluate the thermal resistance constitution for multiple emitters LD. The thermal resistance network model was adopted to characterize the thermal behavior of LDs with one, two and four emitters respectively. The experiment result shows that chip level thermal resistance of multiple emitters LD decreases in proportion to the number of emitters, while the package level thermal resistance remains unchangeable. The study provides an important reference for the thermal design of multiple emitters LD.