Evanescent-field coupling based on long-period fiber grating (LPG) and bi-conical tapered fiber is proposed and investigated both theoretically and experimentally. The light coupled to the cladding modes by LPG can be transferred to a bi-conical fiber. In order to obtain high coupling efficiency, the phase-matched condition should be satisfied and the two fibers should be close enough. The characteristics of the coupling also depend on the position of the coupling region. To get higher coupling efficiency, the coupling region should locate after LPG. This kind of evanescent-field coupling can be used to monitor the characteristics of the LPG which is used in the devices or systems on line.