The imaging neutral particle analyzer (INPA) based on scintillator (ZnS:Ag) has been designed and used on HL-2A tokamak to investigate the distribution of energetic particles (EPs) and even their interactions with magnetohydrodynamic instabilities. The collimation system is composed of a pinhole of 3 mm in diameter and six circular carbon microcrystal diaphragms with a thickness of 10 nm. The neutral particles escaped from six certain positions in the path of neutral beam injection and with a certain pitch angle will pass through the collimator system, and the neutral particles will become fast ions after crossing the carbon microcrystal diaphragm. The fast ions will hit the scintillator after the 180° deflection by the edge magnetic field. The energy, population, pitch angle and birthplace can be calculated by the position and light intensity of the impact spots. The images of impact spots caused by long-lived mode are recorded by a high-speed camera through the fiber optic bundle. The long-lived mode instabilities are approved to be excited by the core EPs with energies, pitch angles and the birthplace of <i>E</i>~12.5-32 keV, <i>v</i><sub>||</sub>/<i>v</i>~0.86 and <i>R</i>~170.5-171.5 cm.