Abstract: Weapons such as long-range detection phased array radar require digital, high power, modular and high-integrated technolgies for their T/R modules. In order to reduce voltage drop in large current transmission of high power front-end T/R modules and the low thermal resistance assembly of high power gallium nitride transistor, this paper uses advanced integrated process technologies, such as nano silver sintering, high permittivity thin-film substrate, and high-density packaging, to meet small voltage-drop of high power modules in high current transmission, miniaturization of matching circuit in GaN die and high efficiency heat dissipation in high temperature environment, etc. An S-band high power and high integration front-end T/R module is developed based on high-power GaN dies. The output power of the module is greater than 500 W, the additional transmission efficiency is greater than 52%, the large current transmission voltage-drop is less than 0.25 V@20 A, the receiving gain is great than 23 dB, the noise figure is less than 2.2, the volume is 63.5 mm×30 mm×10 mm and the weight is less than 35 g. The result shows the front-end module has excellent performance and very strong practical significance.