Abstract: The effects of INA bacteria inoculation on “Zaozhong No. 6” pulp cell ultrastructure under freeze stress in young loquat fruits were studied with simulated low temperature. Results showed that INA bacteria aggravated damage to young fruit pulp cell wall, chloroplast and mitochondrial of loquat. INA bacteria inoculation damaged chloroplasts the most, followed by cell walls, mitochondria. INA bacteria inoculation caused chloroplast cell damage via intracellular freezing at -1 ℃. Different degrees of intercellular freezing also occurred in fruits without INA bacteria inoculation. INA bacteria inoculation damage was stronger at -3 ℃ than at -1 ℃. It therefore indicated that INA bacteria inoculation increased frost damage under low temperature conditions.