BACKGROUND Although previous studies have confirmed the feasibility of magnetic compression anastomosis (MCA), there is still a risk of long-term anastomotic stenosis. For traditional MCA devices, a large device is associated with great pressure, and eventually increased leakage. OBJECTIVE To develop a novel MCA device to simultaneously meet the requirements of pressure and size. METHODS Traditional nummular MCA devices of all possible sizes were used to conduct ileac anastomosis in rats. The mean (± SD) circumference of the ileum was 13.34 ± 0.12 mm. Based on short- and long-term follow-up results, we determined the appropriate pressure range and minimum size. Thereafter, we introduced a novel "fedora-type" MCA device, which entailed the use of a nummular magnet with a larger sheet metal. RESULTS With traditional MCA devices, the anastomoses experienced stenosis and even closure during the long-term follow-up when the anastomat was smaller than Φ5 mm. However, the risk of leakage increased when it was larger than Φ4 mm. On comparison of the different designs, it was found that the "fedora-type" MCA device should be composed of a Φ4-mm nummular magnet with a Φ6-mm sheet metal. CONCLUSIONS The diameter of the MCA device should be greater than 120% of the enteric diameter. The novel "fedora-type" MCA device controls the pressure and optimizes the size.