The relationship between the jacking force and the maximum vertical bearing capacity of a single pile is introduced with a method of estimating the maximum vertical bearing capacity of a single pile by use of the jacking force. In the stage of trial piling, friction piles in the saturated soft soil provide a low bearing capacity, since the bearing capacity of the pile is mainly determined by the frictional resistance on the pile sides after the soil is restored. According to results obtained from the static load test, a coefficient called pressure ratio can be derived through dividing the maximum vertical bearing capacity of a single pile by the jacking force on piles. By comparison, the normal pressure ratios are obtained for the Kunming area, which falls between 1.3 and 2 in the case of jacked prefabricated pipe piles, and between 2.5 and 5 in the case of jacked prefabricated square piles. The maximum vertical bearing capacity of a single pile can be estimated with multiplying the jacking force by the pressure ratio. The influence of the soil compaction effect and the excessive pore water pressure on the bearing capacity of piles is briefly introduced. Soil and pore water in the stratum are compacted in sinking the engineering piles, generating the pore water pressure which creates an upward buoyancy and causes the constructed piles to float; thus reducing the bearing capacity of the single pile.