The invention discloses an NOX detection and calibration test system in an HCCI (homogeneous charge compression ignition) engine cylinder. Features of combustion state in the cylinder can be reflected accurately by utilizing ion currents, the signal strength of each circulating ion current can be detected, ion current signals can be converted in to ion current feature signals through an current output and process module, the ion current feature signals are fed back to an ion current-NOX feature signal convert module and are converted into predict NOX emission feature signals by combining with detected NOX emission feature signals, corresponding ion current signal processing parameters can be recorded, and the purpose of achieving a NOX emission calibration can be achieved. Meanwhile, the ion current technology combined with the calibration parameters can be applied in vehicles and motors as a NOX emission detection manner. The NOX detection and calibration test system has the advantages that NOX production detection in the cylinder can be realized, cost is low, response speed is high, and the NOX detection and calibration test system is adaptable to judging and detecting on transient conditions during an engine operating process.