The mechanical properties of lead-free solder (Sn3.0Ag0.5Cu, Sn0.7Cu and Sn3.5Ag) joints and its inner intermetallic compounds (IMC) were measured by nanoindentation. The samples were prepared according to actual reflow soldering condition and service. Using the continuous stiffness measurement (CSM) technique, the values of hardness and elastic modulus for lead-free solder joints and IMC were measured. The creep stress exponents were obtained according to nanoindentation. The result indicates that the elastic modulus and creep stress exponents of IMC of Sn0.7Cu are 2.03 and 6.73 times of lead-free solders. It is reasonable to consider the influence of the IMC layer when evaluating the lead-free solder joints reliability