Abstract  [Objectives]  In order to understand the occurrence regularity of two armyworms in Yuanyang, Henan province, provide reference for the prediction and scientific control. [Methods]  Mythimna separata and Mythimna loreyi were monitored using monitoring lamp from 2020 to 2021, and the population characteristics of them were analyzed from 2018 to 2021. [Results]  The results showed that the 2nd generation of M. separata was the main generation in 2020 (accounting for 52.95% of the total number), while the 1st generation was the main generation in 2021 (accounting for 81.42% of the total number). The 3rd generation of M. loreyi was the main generation in 2020-2021, accounting for 46.27% and 43.10% of the total number, respectively. The results of ovarian anatomy of female moths showed that the low level proportion (grade I-II) in the 1st generation (except 2019) and the 3rd generation (except 2020) of M. separata were high, indicating that these adults mainly migrated outward. The high level proportion (grade Ⅲ-Ⅴ) in the 2nd generation was high, indicating that these adults mainly stayed locally (except 2020). The low level proportion in each generation of M. loreyi was low (less than 25.00%), indicating that each generation was mainly left in the local area. [Conclusion]  There were obvious differences in dynamics and population characteristics between M. separata and M. loreyi in Yuanyang, Henan province.