Abstract: In order to solve the problem of dynamic adjustment of repeating levelling networks covering a vast area,the author starts out from a classical dynamic linear mathematical model,and then derives a basic equation for the dynamic adjustment of repeating levelling networks.On account of the adjustment of free levelling networks without datum,this paper deals with the pseudoobservation adjustment method,and gives a concrete form of the supplementary matrix G^T in performing the overall free-net-adjustment in two periods and has derived different kinds of formulas for accuracy estimating in this case.Finally,two methods for dynamic adjustment are given,when the levelling networks of two periods do not coincide completely.