The invention relates to an air-tight steering telescopic shaft which sequentially comprises an upper rotating shaft, a first universal joint, a telescopic shaft spline sleeve, a telescopic spline shaft, a second universal joint, a lower steering shaft and a third universal joint from top to bottom. The upper end of the upper rotating shaft is connected with a steering wheel through a spline, the lower end of the upper rotating shaft is connected with the upper end of the telescopic shaft spline sleeve through the first universal joint, and the upper end of the telescopic spline shaft is provided with an outer tooth spline. The air-tight steering telescopic shaft has the advantages that a sliding bearing block is connected with a connecting base in a spherical surface hinged mode, the connecting base is installed on a vehicle body floor through a bolt, the contact surface is good in sealing performance, and the sliding bearing block enables the lower steering shaft to run flexibly in each degree of freedom within the use adjustment range.