Aiming at the problem that there are too many false alarms in the current state monitoring strategy of complex industrial systems， a method to detect working state of missile launcher based on the quick hull algorithm is proposed. The normal working space is estimated from given historical normal data points. For a new-collected data point which reveal working state of missile launcher， if it is inside the established normal working space， the missile launcher is in the normal condition and no alarms are raised； otherwise， the missile launcher is in the abnormal condition and alarms will occur. Compared to static thresholds， the proposed method will cause fewer false alarms. The proposed method does well in explanation compared to the latent variable based methods. A two dimensional and three dimensional cases are analyzed by numerical simulation to evaluate the performance of the proposed method. The simulation results show that the physical meaning of the proposed method is clear and the number of false alarms generated is small.