The study surveys 638 high school students of Hsinchu City to explore using behaviors and tendencies of smartphone addition. The conclusion of the research findings is as follows: 1. Smartphone use periods of high school students are: 1-3hours below is 42.95%; 3-5 hours below is 30.09%; 5 hours and above is 8.78%. 2. The top three smartphone using behaviors of high school students are: listening music, messenger, line, what's app), and online surfing learning materials. 3. Five dimensions average of smartphone addition from highest to lowest are: tolerance, compulsive use, time management, withdrawal syndrome, as well as interpersonal and health-related problems. 4. On the classification of smartphone addition, normal level is 26.5%; warning level is 52.5%; dangerous level is 21%.