Abstract: The main light sources used in the clinical treatment of urological surgery are thulium-doped laser, holmium-doped laser, and green laser via the double-frequency from neodymium-doped laser, etc. In recent years, with the improvement of the output power of blue semiconductor laser diodes, 450 nm blue light has attracted growing attention and been applied in bladder tumor resection surgery, offering advantages such as clean cutting, minimal bleeding, and no adverse coagulation of adjacent tissues. This work focuses on the solution for a high-stability fiber-coupled output blue laser source for urological surgery applications. A 350 W fiber-coupled blue semiconductor laser is built by utilizing four 100 W arrayed blue laser units as the light source. The optical field transmission characteristics of the multi-emitter array are analyzed, and the far-field distribution of optical intensity exhibits a dual-peak structure with a peak angle of \arcsin(5\lambda /4\gamma _\rmd). By applying the spatial beam combining technique, we have successfully achieved the cross-interference of the slow-axis beams, thereby obliterating the emission dead zone. A polarization beam combining scheme is performed to rotate the polarization state of one beam from P-polarized to S-polarized, and then combine it orthogonally with another P-polarized beam, resulting in compression of the spacing between fast-axis beams and improved beam brightness. The collimating structure reduces the divergence angles of the fast and slow axes to 0.6981 mrad and 1.0123 mrad, respectively. The fast axis is expanded by a factor of 1.2 to transform the output beam profile into a square shape. Finally, we obtain a blue laser with a power of 358 W, an output fiber of 200 μm/NA 0.22, a beam combining efficiency of 89.5%, an electro-optical conversion efficiency of 31.3%, and power fluctuation less than 0.4%. Using the water-cooled fiber to couple out the light beam, this high-power laser source may serve as an ideal medical solution for clinical treatment in urological surgery.