To investigate the dynamic response characteristics of the Dual Throat Nozzle (DTN) with an expansion section, numerical simulations were conducted to examine the effects of different expansion angles, freestream Mach numbers, and secondary pressure ratios (SPR) on the internal and external flow fields of a two-dimensional dual throat nozzle with a double expansion section, as well as their impacts on thrust vectoring dynamic response performance. The results indicate that the incorporation of an expansion section in the DTN significantly enhances thrust vectoring efficiency compared to conventional DTNs. Under baseline condition, the vectoring angle increased by 57.93%, primarily due to the wall-attachment effect of the mainstream flow and the guidance provided by the expansion section. However, this configuration also led to a decrease in thrust coefficient by 7.29% due to thrust loss. The expansion angle was found to promote vectoring deflection, but further increases in vectoring angle resulted in a decline in vectoring performance. Higher freestream Mach numbers suppressed the deflection of the mainstream, leading to reduced vectoring angles and thrust coefficients. As SPR increased, the thrust coefficient and thrust vectoring efficiency initially improved before declining. In the low SPR range, increases in SPR enhanced the vectoring angle, but beyond SPR = 5, further increases in SPR had minimal effect on vectoring deflection.