The invention discloses an agricultural sickle capable of adjusting the length. The agricultural sickle comprises a housing, an inner cavity of the housing is provided with a fixed plate, slide rods are fixedly connected to both the top and the bottom of the left side of the fixed plate, the ends, away from the fixed plate, of the slide rods are fixedly connected with the inner wall of the housing, two slide covers are arranged at the surfaces of the slide rods in a sleeving mode, the inner cavity of the housing is provided with an extension rod, the sides, close to the slide covers, of the extension rod are fixedly connected with the slide covers, and clamping grooves are formed in the front surface of the extension rod. In the agricultural sickle capable of adjusting the length, through the arrangement and coordinate use of the housing, a pull rod, a cutter head, a connecting block, an antiskid cover, the slide rods, the extension rod, the slide covers, the fixed plate, the clamping grooves, the slide blocks, first through holes, movable rods, a spring and a clamping rod, the problem that an existing agricultural sickle cannot adjust the length is solved, and the agricultural sickle capable of adjusting the length has the advantages that the length can be adjusted, using by a user is facilitated, and the practicability of the existing agricultural sickle is improved.