Abstract: Theoretical and experimental investigation was conducted to explore microscale boiling nucleation characteristics.By using a statistical mechanics approach,the effect of spatial scale on the bubble nucleation in capillary tubes was analyzed and the superheat temperature of liquid heated in capillary tubes was theoretically derived as a function of spatial scale.The boiling phenomena were observed and the nucleation temperatures were measured for four kinds of fluids (water,methanol,ethanol,and carbon tetrachloride) boiled on a platinum wire confined in capillary tubes.The comparisons indicate reasonable coincidence between theoretical findings and experimental observations.