The invention discloses an automatic sampling barrel for pile bottom slurry. The automatic sampling barrel for the pile bottom slurry is simple to operate, convenient to sample and high in speed, and is provided to solve the technical problem that conditions of hole bottom slurry when the hole bottom slurry is adopted in specific gravity measurement of bored concrete pile slurry. The automatic sampling barrel comprises a barrel body, a lead and a bottom sealer. The lead is arranged on the upper side of the barrel body, and a barrel bottom hole is formed in a bottom plate of the barrel body. The bottom sealer comprises a bottom sealing plate and a limiting rod arranged at the bottom of the bottom sealing plate. The bottom sealing plate is arranged in the barrel body, and the limiting rod penetrates the barrel bottom hole to be movably connected with the bottom plate. The automatic sampling barrel is simple in structure; height measurement is not needed, and the automatic sampling barrel is convenient to use; the automatic sampling barrel is made of leftover materials, and cost is saved.