Abstract: With water as the working fluid,experiments were conducted to study the influences of structure parameters of micro-grooves surface on heat transfer during spray cooling in a closed loop system for volumetric flux varing from 0.938 to 12.73 L/(m²·s). Test results indicated that heat transfer was obviously enhanced for micro-grooves surface, however enhanced effects depended on structure parameters of micro-grooves surface and volumetric flux. When the groove depth,width and spacing equaled 0.5,0.4,and 0.6 mm,respectively,the surface had the optimum heat transfer performance at lower volumetric flux(1. 146-1.604 L/(m²·s)). However,for higher volumetric flux(12.73 L/(m²·s)),the optimum groove depth,width and spacing were 0.5,0.2,and 0.4 mm,respectively,whose heat flux reached 202.5 W/cm²,when the wall temperature was80 ℃. The enhanced heat transfer regime about micro-grooves surfaces was given in the view of smooth surface spray cooling and micro channel flow heat transfer. Non-dimensional criterion equations about micro-grooves surface were derived,in which the influence of surface temperature and structure parameters of micro-grooves surface on heat transfer were considered.