The　theory　of　cylindrical　cavity　expansion　has　been　widely　used　in　many　geotechnical　engineering,　such　as　analysis　of　pressure　meter　testing　and　effect　of　pile　driving.　Extended　spatial　mobilization　plane　(SMP)　theory,　which　can　display　the　effects　of　intermediate　principal　stress,　in　combination　of　finite　strain　theory,　is　used　to　analyze　cylindrical　cavity　expansion　problem　in　homogeneous　soil.　An　analytical　procedure　to　determine　average　volumetric　strain　of　plastic　zone　is　developed　according　to　stress　path　hypothesis.　Accordingly,　＇nondimensional＇　plastic　zone　radius　and　factors　of　cylindrical　cavity　expansion　are　estimated　for　varied　rigidity　index　Ir,　Poisson　ratio　v　and　frictional　angle　ψ.　It　is　concluded　that　average　volumetric　strain　decreases　and　＇nondimensional＇　plastic　zone　radius　and　factors　of　cylindrical　cavity　expansion　increase　with　the　increase　of　Ir,　v,　ψ.　Variation　of　ψ　has　significant　effects　on　factors　of　cylindrical　cavity　expansion　in　the　case　of　greater　Ir.　Furthermore,　a　comparative　study　of　the　solutions　based　on　extended　SMP　and　those　based　on　Mohr-Coulomb　is　made　to　examine　the　effects　of　intermediate　principal　stress　on　cylindrical　cavity　expansion　for　various　soils.　The　values　of　factors　of　cylindrical　cavity　expansion　considering　the　effects　of　intermediate　principal　stress　presented　in　this　paper　are　of　great　significance　for　analyzing　in-situ　tests　and　estimating　ultimate　lateral　friction　of　piles.