Given its negative consequence, the high prevalence of smartphone addiction has become a matter for public concern in recent years. This study takes an evolutionary approach to understanding individual differences in one's vulnerability to smartphone addiction and investigate the role childhood adversity and life history (LH) strategies may play in smartphone addiction via various smartphone use motivations. We recruited 956 Chinese university students between the ages of 16 and 28 (M = 19.35, SD = 1.07) who voluntarily completed an anonymous online questionnaire. Results of path analysis showed a significant direct effect of childhood adversity on smartphone addiction. Moreover, childhood adversity was negatively associated with slow LH strategy, which was negatively correlated with smartphone addiction in the path model. Both pastime and social conformity were significant motivation factors, but they had opposite mediating effects on the relationship between slow LH strategy and smartphone addiction. Our findings improved the knowledge of the complex motivational processes between childhood adversity and smartphone addiction from LH perspective. The findings suggest that people with childhood adversity are at-risk for smartphone addiction, but the opposite mediating effects of two motivation factors illustrate the complex influence LH strategies have on human behavior. Various internal mechanisms should be considered simultaneously in future research to develop a more comprehensive understanding of and effective interventions for smartphone addiction.