A dual-channel switch attenuator chip working at 9kHz to 6GHz was designed using 0.15um GaAs process. The chip consists of a straight-through channel and an attenuation channel.The straight-through channel includes a SPDT switch and two parallel PIN diodes, while the attenuation channel is composed of switch-integrated attenuation networks attenuating 40dB, 10dB, and 5dB respectively.In the design process, parallel PIN diodes were used in the straight-through channel to increase the isolation between ports. The attenuation network utilizes pHMTE, a switching transistor with a 0.15um GaAs substrate material, to control the attenuation. After simulation and optimization, the final measured results achieved the following specifications: the insertion loss of the single-pole double-throw switch in the straight-through channel was less than 0.8dB, the insertion loss after paralleling the two PIN diodes was less than 2.7dB, the insertion loss of the attenuation channel in the reference state was less than 0.7dB, the isolation was greater than 30dB, and the attenuation accuracy was lower than ±5 percent. Considering the installation space, the chip packaging dimensions were prioritized to be 10mm x 10mm in length and width, with an adjustable thickness range of 1.6mm to 3mm. The final determined chip package size is 10mm x 10mm x 2mm.