Low-intensity pulsed ultrasound (LIPUS) has been proven to be an effective treatment modality to improve bone fractures, soft tissue regeneration and neuromodulation. Recently, it has been shown for treating mental health diseases. In this paper, a novel wearable LIPUS treatment device, including a wearable headband and a LIPUS generator, is designed. The circuit in the LIPUS generator is specially built to generate LIPUS for stimulating the brain via temples. Considering comfortableness and safety, we designed a flexible cap to cover ultrasound transducer. The custom-made replaceable transducer cap can be refilled by different ultrasound coupling agents. We demonstrated how polyurethane rubber caps filled with different ultrasound coupling agents affect the ultrasound transmission intensity. Milli-Q water is identified to be the best ultrasound coupling agent for the polyurethane rubber cap with about 39.76% LIPUS intensity transmission.