heat generation in the active region leads to high junction temperature that significantly affects electrical and optical properties, reliability and lifetime of high power diode laser arrays. it is of great importance to understand the thermal behavior to improve the devices. compared to conduction cooling techniques, diode laser arrays packaged on microchannel heat sinks have superior capability to dissipate the large amount of heat so as to deliver higher output power and ensure high reliability. in this paper, numerical approach based on finite element method (fem) and computational fluid dynamics (cfd) was employed to investigate thermal properties of microchannel cooled (mcc) high power diode laser arrays. the static and transient thermal behavior of the devices operated in continuous wave (cw) mode at different water flow rates have been studied in detail. the thermal resistance contributed from the laser chip, solder interface and mcc heat sink was revealed. the correlation between thermal resistance and water flow rate was analyzed. the thermal time constants were derived to characterize the three distinct heating processes related to active region, copper heat sink and copper/water interface. non;uniformity of junction temperature across the diode laser array was discussed by thermal crosstalk employing the independent emitter analysis. understanding thermal phenomena in diode laser arrays could offer useful guidelines in optimizing the operating conditions, mcc heat sink structures and packaging architectures for enhanced performance and reliability. © 2016 ieee.