[Aim]  To improve understanding of the population dynamics of the striped flea beetle (SFB), Phyllotreta striolata, an important pest of cruciferous vegetables in greenhouses, and thereby help develop more precise prevention and control strategies for this pest. [Methods]  Two color plates, yellow and green, were used to collect adult SFB from 5:00 to 17:00. The number of SFB collected, and the hourly ambient temperature and relative humidity, were recorded. The results were analyzed with one-way ANOVA and Tukey's HSD tests, and the effects of ambient temperature, relative humidity, and the interaction between these, on SFB activity was verified using stepwise regression, and generalized additive, models, respectively. The effect of plate color plates (yellow vs green), on the number of SFB captured was assessed using an independent sample t-test. [Results]  A total of 2 703 SFB were collected. The number caught in different periods ranged from 0 to 109 individuals, with an average of 0 to (46.20 ± 11.06) individuals captured per hour. Time of day significantly influenced SFB activity (F = 58.03, P < 0.05). Activity was low from 5:00 to 7:00, but gradually increased after 7:00 it to a stable level from 10:00 until 12:00. There was then an explosive peak in activity between 12:00 and 13:00, after which it significantly declined to a stable level until 17:00. Environmental temperature and relative humidity significantly affected activity (r² = 0.390 2, P < 0.05). Below 33.31 ℃, activity was positively correlated with the environmental temperature (r² = 0.349 1, P < 0.05), and there was no obvious change as the temperature continued to rise. Relative humidity was negatively correlated with activity (r² = 0.345 6, P < 0.05). There was no significant difference in the number of SFB captured using yellow or green boards (t = 0.21, df = 5 758, P = 0.85). [Conclusion]  These results clarify the daily activity patterns of the SFB in plastic greenhouses, and thereby provide an important theoretical basis for the monitoring, prevention and control of this pest.