Abstract: In order to predict the boundary layer transition over small wall corner using eN method, numerical simulations and linear stability theory method are carried out to investigate the disturbance evolutions in hypersonic boundary layers for the cases where the expansion and compression angles are 1°,2°,3° respectively with Mach number 4.5 by solving the classic O-S equation(LST) and N-S equation(DNS). The amplitude and growth rate distribution along the flow direction with different frequencies in different angles have been revealed. Meanwhile, a new disturbance was excited when the disturbance evolutions in hypersonic boundary layers for the small expansion wall corner. Based on these findings, the N value should be corrected in the scenario to predict the transition location with a small wall corner by using the eN method combined with stability analysis, and a correction factor of N value was presented in this work.