Pore water pressure is an important parameter to evaluate the deformation and stability of loess deep filled ground. In order to explore the law of pore water pressure increase and dissipation in the loess deep filled ground in the gully terrain, the pore water pressure monitoring and analysis were carried out in the construction period and later period of a loess deep filled project. The results show that in the analysis of the law of the increase and dissipation of the excess pore water pressure, the change of the hydrostatic pressure caused by the compression of the soil layer and the change of the groundwater level must be deducted; the pore water pressure is affected by the groundwater level and the filling load, and its increase and dissipation modes are mainly divided into three types: the immediate change type, the gradual change type and the non-change type; when the filling speed of earthwork construction is fast, the pore water pressure increases rapidly, on the contrary, the pore water pressure increases slowly or even dissipates; the increment of pore water pressure ∑△u and the increment of fill thickness ∑△p in the construction period are approximately linear relationship, the coefficient of pore water pressure K_u is less than 0.2, and the soil is always in a stable state; the dissipation of pore water pressure is slow in the later stage of construction, and it takes a long time for the settlement to reach stability.