The invention provides an anti-retreating device and a packer with the same. The anti-retreating device comprises a mandrel, a clamping assembly and a cylinder sleeve. A mounting hole is formed in theouter wall of the mandrel. The clamping assembly is arranged in the mounting hole and provided with an elastic part abutting against the mounting hole, and a column body abutting against the elasticpart. The mandrel is sleeved with the cylinder sleeve, the cylinder sleeve can move relative to the mandrel, a clamping groove capable of being matched with the column body is formed in the inner wallof the cylinder sleeve, and the anti-retreating device can provide large anti-retreating force.