Objective: The objective is to study the effect of continuous nursing on the vomiting of patients with expectant vomiting of lung cancer, and to establish a three-dimensional segmentation model of PET-CT image, so as to provide an effective nursing intervention for patients with expectant vomiting of lung cancer. Methods: In this study, the sampling method is adopted. We collected 68 patients (over 18 years old) diagnosed with lung cancer from May 2016 to June 2018 as the study subjects. Patients are divided into experimental group and control group. Before discharge, the patients in the control group are given general discharge guidance and health knowledge guidance. The patients in the experimental group are treated with continuous nursing until the next admission, except for general discharge guidance and health knowledge guidance. The cycle is a period of intermittent chemotherapy. According to the general data questionnaire designed by the researchers themselves, the criteria of acute and subacute toxicity of anticancer drugs developed by the World Health Organization (WHO), and the simple coping style questionnaire, the data are collected. SPSS 22.0 is used for analysis. The rank sum test is used in the grading of expected nausea and vomiting. The score of self coping ability is compared within the group by paired sample t-test, and P < 0.05 is statistically significant. Results: First, before continuous nursing, there is no significant difference in the expected nausea and vomiting between the two groups (P = 0.299). After continuous nursing, in the experimental group, nausea and vomiting is significantly improved (P < 0.001). Second, the positive and negative coping scores of the two groups are 15.98±1.11 and 16.99±1.23, respectively. There is no significant difference between the two groups (P > 0.05). After continuous nursing, the experimental group is compared with the control group. There is a significant difference between positive coping score (19.21±2.12) and negative coping score (16.27±1.53) (P < 0.01). Thirdly, the pixels with the standard uptake value (SUV) > 1/4 of the maximum standard uptake value (SUVmax) are selected as the basic tumor range, which can accurately predict the tumor size and range. Conclusion: PET-CT image analysis and continuous nursing can reduce the degree of nausea and vomiting in patients with lung cancer expectant vomiting, predict the size of lung cancer tumor, improve the patients’ self-response ability and the cure rate of tumor, which is worth promoting in patients with lung cancer expectant vomiting.