The economic efficiency and emission performance of a lean combustion gasoline engine are significantly impacted by duration of rich period and NO

x

breakthrough in the LNT(lean NO

x

trap). Modeling for NO

x

adsorption and desorption process is conducted considering different phases of the LNT working cycle. The experimental data are set as the inlet boundary conditions

the reduction effects of three classical reduction agents

H

2

CO and C

3

H

6

and the regeneration capacity during continuous working cycles are analyzed based on the ash core model theory. The results show that H

2

has the best reducing

ability

followed by CO

and C

3

H

6

the worst. The LNT is able to work continuously with H

2

and CO as the reduction agents. The NO

x

breakthrough during the switch

which is a key factor to determine the reduction ability of CO

can be decreased by increasing the concentration of water vapor in the exhaust gas to improve the overall efficiency of LNT.