[Objectives]  To provide a theoretical basis for forecasting outbreaks of Trichagalma acutissimae (Monzen) (Hymenoptera: Cynipidae), an important pest of Quercus variabilis trees in the Taihang Mountains, China, and to develop integrated pest management methods for this species. [Methods]  The population dynamics and influence of ecological factors, such as slope position, slope aspect and altitude, on sexual and asexual generations of T. acutissimae was systematically studied for five consecutive years between 2012 and 2016. [Results]  (1) Slope position and aspect had little effect on numbers of the sexual and asexual generations; (2) There was a strong, negative relationship between altitude and T. acutissimae abundance; (3) The further young forest was from old forest, the fewer the number of asexual generation galls; (4) There were significant differences in the abundance of T. acutissimae between 2012 and 2013; (5) The equation for a linear model of the relationship between abundance of the sexual generation and altitude in 2012 is: y = 15.80x + 46.85, r=0.939, and the corresponding model for the asexual generation in 2013 is: y = 2.128x - 2.186, r=0.930. [Conclusion]  These models indicate that T. acutissimaeis in the Taihang Mountains is mainly distributed at elevations from 500 to 800m. The rate of expansion of T. acutissimae is no more than 1 000 m a year. Extremely low mid-April temperatures are an important ecological factor affecting the population dynamics of T. acutissimae.