Electrothermal microgripper is a typical execution unit in MEMS micro operation systems. But influenced by the drive mode， parallel-beam electro-thermal microgripper suffers the problem of high temperature at the tip clamping fingers， which may seriously restrict the scope of application. To solve this problem， an analysis on the heat transfer effect is carried out for optimizing the design. Since feature sizes of electro-thermal microgripper is far smaller than the routine and few studies are conducted on micro-scale heat transfer characteristics of electrothermal microgripper， the heat transfer mechanism of electrothermal microgripper is analyzed first to obtain the fitting heat transfer parameters at microscale by experiments. Then， a heat dissipation structure with an S-shaped beam is designed for traditional tip clamping fingers of electro-thermal microgripper， and the optimized effect of the micro gripper is characterized with a micro-infrared analyzer. Finally， the reliability of the optimized design is verified through microsphere gripping experiment. The results show that the heat transfer coefficient of natural air convection is 60 to 300 times than that in macro state. The optimized design based on this can reduce the temperature of tip clamping fingers by about 45%. The proposed optimization scheme is applicable to electro-thermal microgripper of other materials or structures.