In order to solve problems of preparing products with completed shape，high cost of production andpoor repeatability of Al N ceramics，gelcasting and pressureless sintering method were used to prepare Al N ceramicswith nontoxic chitosan system and with Y2O3+ Ca F2as sintering additive． The viscometer，X-ray diffraction and scanning electron microscopy were used to investigate the properties of Al N ceramic slurry and the microstructuresand thermal properties of Al N ceramics． The results show that glutaraldehyde concentration，p H value and chitosancontent have and influence on the gelation time． Vacuum processing is benefitial to removing air bubbles． Y2O3+Ca F2sintering additive not only reduces the sintering temperature，but also effectively improves the thermal conduc-tivity of Al N ceramics． Thermal conductivity of the pressureless sintering Al N ceramics with 52vol． % solid contentcan reach 95. 6 W / ( m·K) ．