The Mg-3%Al melt was inoculated by carbon with different holding time. The effect of holding time on grain refining efficiency was evaluated. The solidification characteristics of the carbon-inoculated Mg-3%Al melt with different holding time was assessed by computer-aided cooling curve analysis. Mg-3% Al alloy could be effectively refined by carbon inoculation. Slight fading phenomenon occurred with increasing in the holding time to 60 min. Carbon inoculation could significantly influence the shape of cooling curves of Mg-3%Al melt. The nucleation starting and minimum temperatures increased. The recalescence undercooling and duration decreased to almost zero after carbon inoculation. The grain refining efficiency of carbon inoculation could be assessed by the shape of the cooling curve and solidification characteristic temperatures, including nucleation starting and minimum temperatures(Ts and tmin)， recalescence undercooling (Δ Trec) and duration.
