Flameless combustion is one of the new high-efficiency and low-pollutant combustion technologies widely concerned in recent years. Due to the volumetric combustion zone with relatively low reaction rate and typically medium or low temperature region in flameless combustion，it is necessary to consider the turbulence-chemistry interaction coupled with detailed reaction mechanisms in numerical simulations to improve the prediction accuracy of the combustion and NO formation. In this paper，the high-fidelity numerical simulations on the flameless combustion of pulverized coal and NO formation were performed based on the dynamic adaptive chemistry mechanism. The dynamic adaptive mechanism simplification algorithm was adopted to realize the local reduction of the in-house-developed nitrogen-containing skeletal mechanism during simulation. It is found that compared with the simulation with a skeletal mechanism，the dynamic adaptive chemistry can obtain nearly three times calculation acceleration without sacrificing the accuracy. And the prediction accuracy of in-furnace NO formation is significantly improved relative to the traditional NO post-processing simulation method. After experimental validation，the distributions of typical in-furnace nitrogen-containing precursors such as HCN and NH3 were obtained. The key information on nitrogen conversion，such as fuel nitrogen conversion pathway，active species and reactions in the furnace，were further analyzed. The results show that the NO formation from pulverized coal flameless combustion mainly depends on NH3，HCN，and N2O intermediates，while NCO and HNO are the key intermediate components. HCN is converted to NO mainly by the HNCO/CN and NCO paths. NH3 is converted from HNCO，and is further converted to NH2 and HNO，and finally leads to NO formation. The N2O path mainly participates in the NO reduction and is insignificant to the NO formation. CH3CN is also an important intermediate component for NO formation，which can be converted to NO by the NCO path.