Breast ultrasound tomography imaging (BUTI) is a new ultrasound imaging technique developed in recent years. In contrast to traditional ultrasound, BUTI uses a ring transducer to surround an object in a water tank and transmits the ultrasound echo from each element sequentially while receiving all the reflective and transmission signals from all elements. The tomography image is reconstructed using a similar reconstruction technique like x-ray computed tomography (X-CT) but much complicate due to the echo travelled along the curve instead of straight line like X ray. In this paper, with the objective of developing a breast ultrasound screening product, in vitro- and in vivo evaluation experiments were performed before proceeding to formal clinic trials. For the in vitro evaluation, a Breast Ultrasound Needle Biopsy Phantom from Supertech, IN, USA, was scanned by BUTIS (Breast ultrasound tomography imaging system) developed in HUST (Huazhong University of Science and Technology, Wuhan, China), MRI and traditional ultrasound scanner. Their image qualities were compared. In addition, the spatial resolution was estimated by using a nylon wire phantom. The results demonstrated that the spatial resolution of BUTIS is over 180 μm, which is almost 1 order higher than the traditional ultrasounds with the same frequency transducer. The in vivo evaluation was composed of a human arm and leg, the breast of a pregnant goat as well as human breasts from a female volunteer. The experimental results demonstrated that BUTIS can not only obtain exceptionally high contrast and high resolution images of soft tissue like the breast in vivo both for animal or human volunteer, but it can also be used to scan the subject with bones inside such as human arms and legs, which seems impossible for traditional ultrasounds. It illustrated that BUTIS will become a new efficient ultrasound imaging technique with wide potential applications in clinics.