Objective. The aim of this study is to investigate the effect of paclitaxel combined with doxorubicin hydrochloride liposome injection (DHLI) in the treatment of osteosarcoma and the MRI changes before and after treatment. Methods. A total of 108 osteosarcoma patients treated in our hospital (January 2020–April 2022) were selected to carry out a single-center retrospective study. Among them, 54 patients receiving the combination chemotherapy (MDT) with high-dose methotrexate, ifosfamide, cisplatin, and ADM were selected as the control group (COG), while 54 patients receiving MDT with high-dose methotrexate, ifosfamide, cisplatin, paclitaxel, and DHLI were chosen as the study group (STG). The COG and STG had the same dose intensity and chemotherapy cycles, and clinical and MRI evaluations were performed after treatment. Results. The evaluation of postoperative clinical efficacy showed that the disease control rate (DCR) of the STG was markedly higher than that of the COG (
P
<
0.05
). The incidence of cardiac toxicity was remarkably lower in the STG than that in the COG (
P
<
0.05
), with no between-group differences in the incidence of fever, abnormal liver function, myelosuppression, stomatitis, and alopecia (
P
>
0.05
). Obvious differences were found in the semiquantitative parameters of MRI in the STG before and after chemotherapy (
P
<
0.05
) and were also found in the SImax, TTP, SEE, PPE, WOR, and R values in the COG before and after chemotherapy (
P
<
0.05
). After chemotherapy, statistical differences were observed in the semiquantitative parameters of MRI between the two groups, with lower parameters such as Slope, SImax, SEE, and R values and higher parameters such as TTP, PPE, and WOR values in the STG than those in the COG (
P
<
0.05
). Conclusion. Paclitaxel combined with DHLI has definite efficacy in osteosarcoma chemotherapy, which is conducive to narrowing the lesion, controlling the disease, and reducing the occurrence of cardiac-related risk events. In addition, the semiquantitative parameters of dynamic contrast-enhanced MRI (DCE-MRI) have a high predictive value for the efficacy of chemotherapy, which can reflect the degree of tumor necrosis and contribute to a timely and objective assessment of the efficacy of osteosarcoma chemotherapy.