Under the smart elderly service model oriented to the integration of medical care, the work aims to study the perception of elderly users'' morphological preferences and emotional expressions of elderly escort robots to reduce users'' barriers to use and distrust of robots. Literature analysis was used to put forward six design principles for the emotional expression of the child-like characteristics for the elderly escort robot CareBot. The statistical analysis of questionnaires was conducted through an experimental study of interaction with robots, and a visualized data report was formed to explore the results of users evaluating the robot. Participants were most able to identify three of these emotional expressions (enthusiastic, indifferent and surprised), and participants'' age and familiarity with children or smart products could have a significant effect on the evaluation results. At the same time, the robot had a child-like characteristic morphology with big-eyed expressions, cute movements, and children''s voices, which was more affinity to the elderly. The applicability and consistency of "expression" and "combination of expression and voice" in the principle of emotional expression were high. Therefore, the appropriate child-like characteristics can enhance the robot''s emotional expression, and the design that increases the robot''s positive emotional expression and decreases the negative emotional expression can help improve the acceptance of elderly service robots.