The emission of NO

x

during coal combustion contributes to the formation of acid rain and photochemical smog

which would seriously affect the quality of atmospheric environment. Therefore

the decrease of NO

x

is of great importance for improving the efficient utilization of coal. The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation. Firstly

in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded. The influence of temperature

atmosphere

heating rate and catalyst on formation of NO

x

precursor and nitrogen migration path at the molecular level were summarized; Secondly

during the process of combustion:the influence of temperature

ambient oxygen concentration

physical structure of coal char

catalyst on heterogeneous oxidation of char (N) were summarized; The effects of char surface properties

catalyst and ambient atmosphere on heterogeneous reduction of NO

x

were also concluded. Based on the quantum chemical cal

culation

the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NO

x

were described in detail. Current studies focus more on the generation of HCN and NH

3

but in order to reduce the pollution of NO

x

from the source

it is necessary to further improve the process conditions and the optimal formula of producing more N

2

during pyrolysis

as well as clarify the path of the generation of N

2

. Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.