One of the most promising ways to detect dark matter is to look for its annihilation or decay products among cosmic-rays. Especially, it is found that quite strong constraints can be imposed by the gamma-ray measurements of dwarf spheroidal galaxies. However, recent studies reveal that these constraints are largely affected by the uncertainty of the dark matter halo density. In this talk, we will discuss the robustness of the dark matter halo estimation especially focusing on the effect of the non-sphericity and contamination of foreground stars.