Microfiber Bragg grating sensors hold great promise given their compactness and large evanescent field effect. The fabrication method of the sensors plays a pivotal role in determining the performance. In this study, a novel approach for batch manufacturing microfiber Bragg grating sensors was proposed using a NaOH solution under hydrothermal conditions. Compared to other methods, it is simpler, safer, and more efficient. Through precisely controlling the reaction time, 50 microfiber Bragg grating sensors were produced with smooth surfaces, exhibiting a surface roughness of about 87 nm, and achieved tailored fiber diameters with an error of only ± 1.2918 μm. In addition, the sensors with different diameters produced by the method to systematically investigate the effects of diameter reduction on various aspects, including spectral characteristics, temperature, strain, refractive index sensing, and bending performance, accompanied by theoretical explanations.