Investigation has been carried out on the thermal performance of sintered miniature heat pipes with 3mm outer diameter. In the theoretical analysis, the influence of wick structure parameters is determined by using the theory of capillary limitation. As a result, the degree of importance is found to be as follows: porosity, powder diameter and thickness of wick structure. In the experiments, heat pipes with sintered dendritic copper powder wicks were fabricated and tested. The maximum heat transfer rate is about 13W with an effective heat pipe length of 20cm. By adopting the formulae developed for both sintered spherical powder and fiber and adjusting their proportion, the agreement between experimental results and prediction is found to be quite good in the tested operation temperature range.