A velocity interferometer system for use with an arbitrary reflector was used to measure the free surface velocity history of LY12 aluminum alloy in a wide range of pre-heating from the room temperature approaching to the melting point, and the dependences of dynamic yield strength and spall strength on the initial sample temperature have been investigated. Experimental results indicate that the dynamic yield strength decreases rapidly with the heating temperature, and only 15% of the initial strength at room temperature is retained when heated up to 847K (86K lower than the melting temperature). The measured yield strength has been compared with the Zerilli-Armstrong (ZA) model and Steinberg-Cochran-Guinan (SCG) model calculation, which points out that the ZA model could describe the dependence of the yield strength on temperature well and the SCG model has overestimated the dynamic yield strength at high temperature significantly. Decrease of the spall strength with the increase of heating temperature for LY12 aluminum alloy was observed also, and nearly 80% loss of spall strength was determined in the present experimental temperature range of 296—847 K. An empirical formula has been proposed to normalize the dependence of spall strength on the heating temperature, and it gives a fairly good fitting for a number of aluminum based materials, including pure aluminum, aluminum alloy and single crystal aluminum, measured in this work and by others in the literature.