The ‘Qianmilong’ pitaya fruit variety was used to study the factors affecting the effects of mulching on the rhizosphere soil and the quality of pitaya fruit. Pineapple residue generated from intercropping in pitaya orchards was used for mulching treatment （SM）， with no mulching as the control （CK）. Samples of soil and fruit were collected after one year of coverage to analyze the effects of mulching pineapple residue on the physicochemical properties， activity of enzyme， structural diversity of microbial community in rhizosphere soil， and the quality of pitaya fruit. The results showed that，compared to the control，mulching increased soil organic matter content by 119.26% and significantly enhanced overall soil nutrient levels .The activities of nitrate reductase，urease，cellulase，and sucrase significantly increased by 107.37%、13.70%、16.37% and 25.74%，respectively.Regarding fruit quality，single fruit weight，total soluble solids，soluble sugar，and titratable acid increased by 22.10%，5.80%，3.25%，and 11.76%，respectively.Mulching significantly increased the relative abundances of bacterial phyla Proteobacteria and Acidobacteriota and fungal phyla Ascomycota and Basidiomycota by 20.35%，15.81%，12.08% and 58.58%， respectively.The relative abundances of bacterial Chloroflexi and Actinobacteriota were significantly reduced by 16.13% and 12.97%，respectively. The results of Alpha diversity analysis showed that mulching had no significant effect on the bacterial communities in soil. The Shannon index， Simpson index， Invasimpson index， and Pielou index of fungal communities in SM significantly increased by 37.72%， 15.66%， 61.42%， and 60.00% compared to that in CK. The results of correlation analysis and structural equation modeling showed that the alkali-hydrolyzable nitrogen in soil was the primary factor driving the content of total soluble solids and titratable acid in pitaya fruit， followed by the activity of urease in soil. It is indicated that the measure of mulching pineapple residue can significantly increase the content of organic matter in soil， promote the proliferation of bacterial and fungal communities in soil， regulate the structural diversity and abundance of microbial community in soil， positively improve the content of alkali-hydrolyzable nitrogen and the activity of urease in soil， and enhance the yield and intrinsic quality of pitaya fruit.