  In this work we study the constraints on the dark matter interaction with the
standard model particles, from the observations of dark matter relic density,
the direct detection experiments of CDMS and XENON, and the indirect detection
of the antiproton-to-proton ratio by PAMELA. A model independent way is adopted
in the study by constructing the effective interaction operators between dark
matter and standard model particles. The most general 4-fermion operators are
investigated. We find that the constraints from different observations are
complementary with each other. Especially the spin independent scattering gives
very strong constraints for corresponding operators. In some cases the indirect
detection of antiproton-to-proton data can actually be more sensitive than the
direct detection or relic density for light dark matter (less than 70 GeV).
