The utility model provides an interior differential cylinder structure belongs to the hydraulic transmission technology field. This interior differential cylinder structure includes: the hydro -cylinder body, including a hydro -cylinder section of thick bamboo and respectively demountable installation at protecgulum, the hou gai at hydro -cylinder section of thick bamboo both ends, a hydro -cylinder section of thick bamboo, protecgulum, back lid three surround and form section of thick bamboo chamber, the piston rod, movable mounting is at section of thick bamboo intracavity and pass the protecgulum, the piston rod is inside to undercut, the piston is installed at piston rod terminus, section of thick bamboo chamber and back section of thick bamboo chamber before the piston divide into section of thick bamboo chamber, differential pole, differential pole rear end is installed and is covered after, the setting of differential pole front end is in the piston rod and form differential chamber. This interior differential cylinder structure has overall arrangement compactness, safe and reliable's advantage.