The invention discloses a pre-alarming method and a pre-alarming device of optical cable problems. The method includes: optical time domain reflectometry (OTDR) curves of optical fibers contained in a specified optical cable section are obtained through detecting; for each optical fiber in the optical cable section, whether the optical fiber meets the preset condition is judged respectively according to the OTDR curve of the optical fiber and the pre-stored preference curve of the optical fiber; when the OTDR curve of at least one optical fiber in the optical cable section meets the preset condition, a pre-alarming signal aiming at the optical cable problem of the specified optical cable section is generated and output; and the preset condition is used for determining that the optical fibers have performance degradation problems. The method and the device can achieve pre-alarming of the optical cable problems.