Silicon nitride (Si3N4) ceramics are considered to be one of the most promising ceramic substrate materials due to their good insulation, low coefficient of thermal expansion and high mechanical properties. However, the thermal conductivity of Si3N4 ceramics prepared by conventional methods is low (< 50 W·m–1·K–1), which greatly affects the reliability of chips and even causes the failure of electronic devices. New methods such as gas pressure sintering (GPS), and sintered reaction-bonded silicon nitride (SRBSN) have been employed to fabricate Si3N4 ceramics with high thermal conductivity and high bending strength. Nevertheless, the sintering temperature of both GPS and SRBSN is high and the holding time is too long, which lead to the high cost and limit its applications. Spark plasma sintering (SPS) can produce ceramics with high density in a relatively short time, while the short soaking time is not suitable to improve the thermal conductivity. High-temperature heat treatment can promote the growth of Si3N4 grains, and thus improves the thermal conductivity of Si3N4 ceramics. Therefore, it is expected that Si3N4 ceramics with highbending strength and high thermal conductivity can be prepared at a lower temperature and a shorter time by the combination of SPS and high-temperature heat treatment processes.