This study focused on the organs of the semi-parasitic medicinal plant Monochasma savatieri Franch. ex Maxim., the organs of its host Loropetalum chinense (R. Br.) Oliv., and the rhizosphere soil of M. savatieri. The methods of allometric growth analysis and redundancy analysis were applied to investigate the stoichiometric characteristics and coupling relationships of carbon (C), nitrogen (N), and phosphorus (P) in the "rhizosphere soil-M. savatieri-host plant" continuum. The aims were to reveal the nutrient flow patterns in the "rhizosphere soil-M. savatieri-host plant" continuum, to identify nutrient limitations, and to analyze the nutrient utilization strategies of both M. savatieri and its host plant. The results indicated that: (1) the rhizosphere soil of M. savatieri was characterized by high levels of C and N but a lack of P content. In addition, the rhizosphere soil of M. savatieri showed a low level of efficient utilization of soil nutrients. According to the N/P threshold hypothesis, both M. savatieri and its host were primarily limited by P. (2) The allometric growth analysis revealed that the accumulation rate of nutrient elements in the organs of M. savatieri was CM. savatieri and the leaves of the host had a higher nutritional content and a better utilization efficiency compared to the other organs. (3) M. savatieri displayed higher N and P content, as well as lower carbon to nitrogen (C/N) and carbon to phosphorus (C/P) ratios compared to the host, indicating that it took a resource-acquisitive strategy. On the other hand, the host exhibited advantages in C fixation, reflecting that it employed a resource-conservative strategy. (4) A stronger correlation was observed between the nutrient levels of M. savatieri and its rhizosphere soil than that between M. savatieri and its host within the "rhizosphere soil-M. savatieri-host plant" continuum’s stoichiometric characteristics coupling relationship of C, N, and P. The redundancy analysis revealed that the total nitrogen content and C/P ratio in the rhizosphere soil of M. savatieri, as well as the nitrogen to phosphorus (N/P) ratio of the host root, were the significant factors influencing the chemical stoichiometric characteristics of various organs in M. savatieri. In conclusion, the main source of N and P nutrients for M. savatieri appears to come from its rhizosphere soil rather than from the host plant. Therefore, it should be beneficial to the artificial cultivation of M. savatieri by appropriately supplying N and P fertilizers, particularly P fertilizers, in the soil.