An　encoding　algorithm　is　proposed　for　three-dimensional　(3-D)　information　using　optical　asymmetric　cryptosystem　and　the　digital　interferometry.　3-D　information　can　be　treated　as　an　ensemble　composed　of　multiple　points,　and　every　point　spreads　in　a　spatial　limited　field.　Due　to　the　free　space　coordinates,　the　encryption　system　of　3-D　information　can　be　regarded　as　an　optical　asymmetric　cryptosystem.　We　encrypt　3-D　information　with　the　double　random　phase-truncated　encoding,　and　then　record　the　amplitude　of　ciphertext　by　digital　interferometry.　Computer　simulations　demonstrate　the　feasibility　and　effective　of　the　proposed　method.　This　cryptosystem　is　also　numerically　tested　with　the　incorrect　keys,　the　addition　noise　to　the　ciphertext,　and　spatial　information　occluded　ciphertext.　The　proposed　algorithm　has　three　advantages:　the　high　efficiency　of　encryption,　the　safety　provided　by　one　added　dimension,　the　increasing　information　quantity　and　the　optical　asymmetric　cryptosystems.　The　high　robustness　to　the　system　is　also　achieved.