Abstract: To discover the sealing of low vacuum preloading by using muck instead of sealed films and the transfer rules of vacuum degree in muck foundation, monitoring instruments are embedded for treatment of super-soft muck foundation project, and field tests are performed. The results show that the requirements of sealing are satisfied by using muck instead of sealed films. The vacuum degrees in drainage and muck both decrease with the depth, and the decrease speed of the vacuum degree in the drainage has a close relation with the properties of the muck around it. The vacuum degree in the muck is obviously less than that in the drainage, and there exists a startup process. The loss of the vacuum degree transfer in new hydraulic fill muck is obviously larger than that in the muck.