Abstract Public bike system (PBS) improves mobility in a healthy, emission-free, and congestion-reducing way. Various studies have examined the characteristics of PBS. Hitherto, there lacks a quantitative analysis directed to the effects of the newly emerged dockless bike-sharing system (DBSS) on the PBS. To fill this gap, this paper takes Nanjing PBS as a case study, to explore the changes of PBS usage after the popularity of DBSS at two levels, including user level and station level. Results show that the DBSS has a greater effect on weekdays than weekends, and in contrast with users over 40 years old, users who are younger, especially those of 21 to 25 years old, have a larger reduction in usage frequency. These findings suggest that the DBSS appeals to young commuters to some extent. Therefore, to improve the efficiency of PBS, more attention should be paid to the improvement of stations where young commuters often borrow and return bikes. As for the impacts of DBSS on the trip duration, there is no significant sexual difference. Notice that the patterns of pickups and returns over the hours of the day remain unchanged after the popularity of DBSS, but for station dynamics over the days of the week, the number of active days is reduced.