The precast concrete assembly foundation for Qinghai-Tibet AC 750 kV/DC ± 400 kV grid interconnection project in frozen soil area was tested under compression load.The mechanical co-working properties for the different parts of the foundation were analyzed based on the monitoring results of structural displacement, soil pressure, and fitting stress. Under compression load, both the displacement and the changing regularity of the ring flange connecting the column and the bottom slab and the joint seam of the two consolidated bottom slabs comformed with that of the top plane of the foundation.Two stages of elastic and elastic-plasticity were observed according to load-diplacement curves of the foundation. The stress of the channel beams increased with the compression load and were found in elastic stress status. Under the compression load, the two edges which were parallel to the the joint seam of two consolidated foundation slabs had a tendency to upwarping. However the displacement of all angular measuring points were less than that of the top plane of the foundaiton. The diplacemnet and the stress of the different connected parts redistributed until the new banance developed. As a result, the different connected parts of the precast concrete assembly foundation co-operated to carry the compression load. The structrual characteristic of the assembly foundaiton, the gaps among the assembly parts, the discrepance of the nut screwing up and the mismathing tolerance during consolidating were the key factors to determine the performance of the foundation. Under compression load, all structural parts of precast concrete assembly foundation had good entirety.