The length of ordinary uniform fiber gratings is gauged in the order of centimeters,which restricts the spatial resolution of the measurement,and produces spectral distortion for the measurement of non-uniform fields,which affects the measurement accuracy. The length of the gate region of the ultra-short FBG is measured in the order of 10~100 μm,which can solve the problems of non-uniform field measurement and spectral distortion. In this paper,the effective length of the grating is greatly shortened by setting the slit diaphragm and adjusting the distance between the mask and the optical fiber,and the ultra short gratings are produced with a length of 0.1 mm,0.2 mm,0.5 mm,and a 3 dB bandwidth of 7.9 nm,4.2 nm,2.1 nm,and a reflectivity of 5 %,10 %,30 %.By adjusting the distance between the mask and the fiber,ultra-short fiber gratings with a gate length of 0.05 mm and a 3 dB bandwidth of 14 nm can be written. In order to suppress the side mode suppression ratio of ultra-short fiber gratings,the grating apodization was performed using a single slit diffraction modulated beam intensity distribution,and the writing of a 0.5 mm grating with a greater than 30 dB side mode suppression ratio is realized.