Internal browning (IB) seriously restricts the development of pineapple industry. Its occurrence is mainly from excessive reactive oxygen species (ROS) causing membrane damage, which breaks the original compartmentalization between plastid polyphenol oxidase (PPO) and phenolic substrates in vacuoles. It polymerizes into quinones after contact with oxidation. The antioxidant clearance system is able to remove excess ROS and maintain the dynamic balance of ROS in the body. In early time, our laboratory used ascorbic acid (AsA) which can effectively delay the deterioration of IB of 'Pairs' pieapple. But the reaction mechanism of AsA is not clear. Ascorbate peroxidases (APX, EC1.1.11.1) are heme-binding enzymes that reduce hydrogen peroxide (H₂O₂) to water using AsA as an electron donor. It is involved in various developmental physiological processes and stress responses in plants. In this study, we selected six APX genes with AsA as the substrate in pineapple to analyze the occurrence process and the ascorbate transcript level changes after the AsA treatment. AcAPX1 was significantly upregulated at 9 d and 12 d after AsA treatment and was significantly different from the control group. It showed that AsA significantly enhanced the AcAPX1 expression. Correlation analysis showed that the incidence index of black heart disease was significantly positively correlated with the AcAPX1 expression level. It is speculated that this gene may play an important role in AsA delaying IB with pineapple. To further explore the mechanism of action, AcAPX1 was cloned from the pineapple pulp. The physicochemical properties and protein domain were analyzed by bioinformatics analysis. The results showed that the open reading frame length was 753 bp, encoding 250 amino acids. The predicted molecular weight of the protein was 27.410 87 kDa, and the theoretical isoelectric point was 5.52. There was no transmembrane helix region, which was a stable hydrophilic protein. Amino acid sequence alignment analysis showed that AcAPX1 of pineapple shared more than 85% homology with papaya, banana, coconut and oil palm. The functional domain analysis of AcAPX1 showed that it had heme binding sites, K⁺ binding sites and substrate binding sites (superfamily: cl00196), belonging to the members of the plant peroxidase superfamily. Cloning of AcAPX1 is of great significance for studying the molecular mechanism of its antioxidant capacity in pineapple and the control of internal browning. This study would lay a foundation for further exploring the molecular mechanism of pineapple AcAPX1 involved in AsA clearing ROS and delaying the deterioration of internal browning.