Antenna on chip (AoC) provides an efficient solution for front-end antenna systems operating in the terahertz (THz) band. It can reduce the interconnection loss between on-chip system circuits and off-chip antennas, effectively enhancing system performance. Meanwhile, there exist some technical challenges, such as narrow bandwidth and low antenna radiation efficiency. In this paper, an improved on-chip dielectric-loaded integrated antenna array is proposed. The feeding network is based on an on-chip high-order mode resonant cavity slot array. In the frequency range from 330.7 GHz to 357.4 GHz, return loss is better than -10 dB, the antenna gain is 6.9～9.7 dBi and the radiation efficiency is better than 71% and especially up to 81.4% at 343.6 GHz. Simulation results indicate that the proposed dielectric-loaded antenna achieves significant improvements over the original on-chip slot array antenna, showing enhanced impedance bandwidth, increased gain and higher radiation efficiency. The integrated scheme significantly improves the reliability of the dielectric-loaded antenna array, and the proposed structure is suitable for THz on-chip array integration applications.