Abstract: In situ test is the most objective and reliable method to obtain design parameters and to understand the mechanism of pile foundations.However,installing earth pressure cells in side faces and strain gauges in piles are difficult problems which have not yet been solved.My colleagues and I study these problems and develop some simple and reliable instruments to be used in the precast piles and bored cast-in-place piles.Furthermore,we produce a combined equipment to apply static and dynamic load on pile top and solve a key problem in the static-dynamic load test of pile.