The purpose of this study was to investigate cognition of life phenomenon on robotic dogs according to properties of robotic dogs amongst aged 3, 4 and 5. 95 Children aged 3 to 5 years participated in this study. Each child was interviewed individually and responded to questions designed to measure his/her cognition of life phenomenon. The major findings of this study are as follows. First, there was a significant difference in children’s cognition of the life phenomenon according to their age. 3 years were more likely to refer the robotic dog as alive, compared to the 5 years. Secondly there was a significant difference in children’s inference of the life phenomenon according to properties of robotic dogs. Such as high activeness and responsiveness, preschoolers considered robotic dogs to be alive and have more biological and psychological traits. This result shows the activeness and responsiveness of robotic dogs influences young children’s inference of life phenomenon.