Internal Reconnection Event (IRE) is a characteristic relaxation phenomenon in STs (Sperical Tokamaks). To investigate the deformation of the plasma shape during IRE, four PIN diode arrays of 20 channels were installed on the TST-2@K (TST-2 at Kyushu University). Precursor of IRE was observed for several milli-seconds. The fluctuation was composed of two dominant components in frequency of 10kHz and 4kHz. The mode structure of 10kHz component is n/m=1/1 helical structure and 4kHz is n/m= 3/4. The overlap of modes (10kHz and 4kHz) was considered to be cause of IRE in TST-2 from the position and the growth of the modes.