Aiming at the problem of the stress and the displacement of the fiber embedded in the flexible optoelectronic substrate can change, which affects the coupling efficiency of the optical path and the effective refractive index of the fiber which can result in the transmission performance to change under lamination process, he finite element method software was adopted to conduct coupling analysis of stress modules, heat transfer and electromagnetic field of fiber embedded flexible substrate. Simulation results show that the maximum stress of the fiber embedded in the trapezoidal groove flexible optoelectronic substrate was 68.336 7 MPa. The fiber displacement embedded in trapezoidal groove is 1.430 4 μm largest among the three types grooves. The maximum stress of the fiber increases from 52.667 MPa to 71.907 MPa with the increasing of groove width. The maximum stress of the fiber increased from 51.589 MPa to 53.567 MPa as groove spacing increases. The maximum fiber stress decreases from 52.667 MPa to 47.793 8 MPa firstly and then increases to 67.349 6 MPa with the increase of groove depth. With the increase of temperature and pressure, the effective refractive index of single-mode fiber in the X direction increased from 1.446 249 977 to 1.446 259 084 and increased from 1.446 326 398 to 1.446 393 041 in the Y direction. The difference of effective refractive index increases with the increas of temperature and decreases as the pressure increases. With the effective refractive index increases, the fiber core's ability to limit light energy increases which can better reduce the radiation of light energy and the bending loss of the fiber. The research conclusion has certain reference value and guiding significance for designing the embedded structure of flexible optoelectronic printed circuit boards.