Objective: To analyze the construction method and effect of a three-tiered prevention service system for hospital weight management under the concept of health ecology. Methods: 1500 researchers who completed this survey from January to December 2025 were selected as the observation subjects. Among them, 1000 researchers implemented primary prevention, 300 implemented secondary prevention, and 200 implemented tertiary prevention. A three-tiered prevention service system for hospital weight management under the concept of health ecology was built based on different groups, and the researchers’ weight, waist circumference, etc. were evaluated before and after the implementation of the system. Results: The weight management awareness rate of researchers who implemented primary prevention in the long term was higher than that of researchers who implemented mid-term and short-term prevention (p < 0.05); the long-term obesity incidence rate of researchers who implemented secondary prevention was lower than that of researchers who implemented mid-term and short-term prevention (p < 0.05); the long-term BMI index of researchers who implemented tertiary prevention was lower than that of researchers who implemented mid-term and short-term prevention (p < 0.05). Conclusion: After the construction of a three-tiered prevention service system for hospital weight management under the concept of health ecology, the implementation of relevant weight prevention strategies for different groups can reduce the obesity rate and reduce the weight of obese individuals, which has application value.