The bend waveguide is one of the key components of photonic integration. In this paper, by using tightly focused femtosecond laser pulses with repetition rate of 76 MHz, pulse duration of 50 fs, average output power about 270mW, and the focus lens NA=0.65, we put forward a structure of waveguide that bent it to be 1/4 round, and research its mechanism by performing experiments. Under the above conditions, when the vertical scanning speed of the laser system is 0.8 mm/s, the width of the bend optical waveguide is about 10 mu m, the loss reaches a minimum value about 1dB/cm when the bend way's radius is about 5mm. Based on the experimental results of the above parameters, we can fabricate a 1/4 round vertical bend fiber coupler, which can be applied to the connection between the chips or inter-level optical. The results showed that the bend lithium niobate waveguides can be applied in the field of optical communication and has important implications for the production of low loss, low cost and small size optical waveguide gratings, vertical fiber coupler, optical switches and other devices
