In　order　to　improve　the　design　and　calculation　of　laterally　loaded　piles,　finite　difference　numerical　analysis　method　which　can　calculate　displacements　and　internal　forces　of　piles　under　lateral　load　of　trapezoid　distribution　is　proposed　based　on　nonlinear　p-y　curve　mode　of　foundation　coefficient.　The　finite　difference　formulations　of　displacements　of　piles　are　deduced　in　detail.　Based　on　these　formulations,　computation　and　visualization　programs　of　displacements,　internal　forces　of　piles　and　soil　reaction　are　developed　for　design　calculations　of　anti-slide　piles　and　cantilever　retaining　piles　for　deep　foundation　pits.　Taking　the　new　pile　cast-in-situ　concrete　thin-wall　pipe　pile　(PCC　pile)　as　anti-slide　pile,　a　comparison　study　is　computed.　The　examples　show　that　this　method　is　convenient　and　reliable.　Numerical　solutions　are　close　to　real　solutions　when　finite　differential　segments　are　small　enough.