the remediation of heavy metal-contaminated soils has attracted increased attention worldwide. The immobilization of metals to prevent their uptake by plants is an efficient way to remediate contaminated soils. this work aimed to seek the immobilization of cadmium in contaminated soils via a combination method. Flask experiments were performed to investigate the effects of hydroxyapatite (HAp) and the Cupriavidus sp. strain ZSK on soil pH and DtpA-extractable cadmium. pot experiments were carried out to study the effects of the combined amendment on three plant species. The results showed that HAP has no obvious influence on the growth of the strain. With increasing concentrations of HAp, the soil pH increased, and the DtpA-extractable cd decreased. Via the combined amendment of the strain and HAP (SH), the DTPA-extractable Cd in the soil decreased by 58.2%. With the combined amendment of the SH, the cadmium accumulation in ramie, dandelion, and daisy decreased by 44.9%, 51.0%, and 38.7%, respectively. Moreover, the combined amendment somewhat benefitted the growth of the three plant species and significantly decreased the biosorption of cadmium. These results suggest that the immobilization by the SH combination is a potential method to decrease the available cadmium in the soil and the cadmium accumulation in plants. Soil is the main sink for metals and acts as a barrier to prevent their entry into the food chain 1. However, human activities such as mining and metal smelting have gradually transferred many toxic metals from the earth's crust to the environment, resulting in the spread and contamination of heavy metals 2-4. In recent decades, heavy metal pollution has become a serious problem worldwide. In China, it was reported that 13.33% of all soil samples collected from 6.3 million square kilometres of land were polluted with high levels of metals 5. Cadmium pollution has been detected in all agricultural areas. Cadmium is chemically stable and does not undergo chemical or microbial degradation. Moreover, cadmium is not an essential element for living organisms. Generally, it is regarded as the most toxic among heavy metals 6. Cadmium in the soil harms plant cells by altering metabolic pathways, damaging chloroplasts and mitochondria, and causing oxidative damage to lipids and proteins 7,8 , and cadmium also interferes with the uptake and transport of essential elements, e.g., P and K 9. Excessive Cd can reduce iron uptake by plants, affecting their photosynthesis 10. Cadmium can also accumulate in plants and animals and thus enters the human body through the food chain, threatening health 11,12. Thus, it is an enormous challenge to remediate heavy metal-contaminated soils worldwide. Various physical, chemical and biological techniques have been used to remediate heavy metal-contaminated soils 1. In situ immobilization is generally considered a feasible technique to remediate metal-contaminated soils due to its cost effectiveness and ease of operation 13. Many researchers have reported on the use of various...