The absorption performance of low-partial-pressure H2S in a monoethanolamine (MEA)-activated N-methyldiethanolamine (MDEA) aqueous solution was investigated. The absorption amount (in mass, g H2S/g solutions) and H2S loadings (mol H2S/(mol MEA + mol MDEA)) were measured, and the apparent absorption rate was determined from the time-dependent absorption capacity. Experimentally, the temperature and partial pressure of H2S (P-H2S) ranged from 303.2 to 323.2 K and from 300 to 500 Pa, respectively. The mass fractions of MDEA (w(MDEA)) and MEA (w(MEA)) ranged from 0.30 to 0.50 and from 0 to 0.075, respectively. The temperature, W-MDEA, W-MEA, and P-H2S dependencies of the absorption performance were analyzed. It is impressive that the addition of MEA significantly enhanced the absorption amount of H2S yet slightly influenced the apparent absorption rate. In addition, a tray column consisting of six plates was used to verify the removal H2S efficiency of low-partial-pressure H2S (P-H2S= 500 Pa) and the results showed that in the case of W-MDEA = 0.5, w(MEA) = 0.075, and T = 313.2 K, the removal efficiency achieved 95% when the ratio of gas to liquid was 40, indicating that MEA-activated MDEA aqueous solutions are promising in the removal process of low-partial-pressure H2S.