Semi-solid metal (SSM) processing requires urgently the development of new or improved alloys that can take its full advantages. Such alloys should have less temperature sensitivity of solid fraction, suitable solidification range, proper potential for age hardening, favourable theological properties and mechanical properties. In this work, thermodynamic calculation is used as the first step of aluminium alloy design for SSM processing to analyse the effects of alloy composition on the temperature sensitivity of solid fraction, solidification range and potential for age hardening, and narrow down the composition range with promising SSM processability.