The instantaneous luminosity of the Large Hadron Collider (LHC) at CERN will be increased up to a factor of seven with respect to the original design value to explore higher energy scales. In order to benefit from the expected High Luminosity (HL) performance, the first station of the ATLAS muon end-cap system will be replaced by a New Small Wheel (NSW) detector. The NSW consists of two types of detector technologies; MicroMesh gaseous detectors (MM) and small-strip Thin Gap Chambers (sTGC) both with good tracking and triggering capabilities. The NSW will provide precise track-segment information to the muon Level-1 trigger system and hence reduce fake muon triggers. This article summarizes the simulation of the NSW trigger decision system, the track reconstruction algorithm implemented into the trigger processor and results of performance studies on the trigger system showing that the NSW will perform well in high luminosity conditions.