In recent years, magnesium and its alloys as biodegradable materials have attracted much attention. Biodegradable MgYREZr, mainly WE43 alloy, with good integrated properties has been studied in favor. In this paper, the microstructure, mechanical properties, biodegradable property and biocompatibility of biodegradable MgYREZr alloy were reviewed, as well as the clinical results of the bone fixation screws developed in Germany using the alloy with similar composition to WE43. MgYREZr alloy presents uniform microstructure and higher mechanical properties after large plastic deformation with the grain size of less than 1 μm. The RE elements can be dissolved and stabilize the corrosion layer, which can decrease the degradation rate of the alloy accompanying with optimized heat treatment. The animal tests showed biocompatibility and good bioactivity. Clinical tests showed the MgYREZr alloy screws presented equivalent to titanium screws for the treatment of mild hallux valgus deformities, however resorption cysts was revealed by X-rays when the acute scaphoid fractures were treated with a double-threaded screw made of MgYREZr, and it was only after 6 months that the fractures were consolidated enough to allow physical work. So for different clinical cases, the degradation and biological behaviors of MgYREZr alloys need to be further studied in vitro and in vivo. To control the degradation rates to meet the different clinical requirements is still a major obstacle for biodegradable MgYREZr alloys to enlarge their clinical application.