Using conventional and unconventional observation data, with NCEP reanlysis data, a largescale continuous high temperature process occurring in North China Plain was studied.Some results were shown as follows: Highpressure (ridge) in the upperlevel, stable hightemperature zone on 850 hPa and the low pressure generated in Northwest China with surface stretching or moving eastward are the causes for the formation and maintenance of the sustained high temperatures process. Meanwhile, the quantitative values of the advection term, perpendicular term and nonadiabatic term leading to local temperature variations are estimated. The advection term varies complicatedly, but it plays a very weak role. The perpendicular term leads to temperature increase by 30% in this process. The local temperature increment is mainly from the nonadiabatic term, and it plays a significant role (about 41% in this process) in local temperature increment. Therefore, in the operational forecast, the role played by advection can be ignored, the perpendicular term and nonadiabatic term should be focused and considered.