Under the horizontal load

it is difficult to detect the size and distribution of prestressed high concrete pile（PHC pile）deflection.This paper introduces the pile deflection method based on Brillouin optical time domain analysis（BOTDA）.A model test about piles flat pushing was designed

and the deflection formula of the pile under the horizontal loads was deduced.Through comparing the simulation and the measurement data

the feasibility and accuracy of the PHC pile deflection detector based on BOTDA was analyzed and the deformation of PHC pile was gained.Applying to project

the feasibility of the method used to measure PHC pile deflection was verified.The result shows:the advantage of PHC pile deflection detection and monitoring by BOTDA sensing technology is obvious;the technology has the characteristic of distributed detection

and can accurately obtain the impact depth of PHC pile under the horizontal loads and its deflection distribution.The method is simple and cost-effective

and sensing fiber is durable.The fine detection and monitoring of pile deflection distribution can be achieved through the technology.It is worth of application and promotion in the detection and monitoring of the pile.