By using the observation data from maize field observation stations during 1981-2005 in Heilongjiang Province, and cluster analysis and typical year analysis methods, this paper studied the lowest temperature limit index of maize field sowing. At the same time, the index was verified with the 2006-2018 observation data and the experiment data from the field sowing by stage. The results showed that the ground temperature is the main factor for the maize sowing, and the daily average ground temperature (10 cm) can be used as an indicator of the minimum temperature limit. The lowest threshold temperature index of the daily ground temperature (10 cm) is 6.0℃, at which the maize cannot be sown. The lowest threshold temperature index of the daily average ground temperature (10 cm) is from 6.0℃ to 8.0℃, at which the maize can be sown, but there is a small number of maize suffering from low temperature disasters. The lowest threshold temperature index of the daily average ground temperature (10 cm) is 8.0℃, at which the maize can be sown safely.