The invention discloses polyurethane foam with ultralow surface hardness and a high press-to-sink ratio. The foam is prepared from a component A and a component B. The component A is prepared from 37-50 parts of polyhydric alcohol 1, 25-50 parts of polyhydric alcohol 2, 0-30 parts of polyhydric alcohol 3, 0-10 parts of polyhydric alcohol 4, 0-18 parts of polyhydric alcohol 5, 0.7-2 parts of surface active agent, 0.4-0.7 part of composite catalyst, 0-5 parts of amine-terminated polyether and 2.5-4 parts of foaming agent. The component B is prepared from 26-42 parts of isocyanate. Polyhydric alcohol 1 is oxirane and epoxypropane copolymerized polyhydric alcohol, polyhydric alcohol 2 is epoxypropane polyether polyol, polyhydric alcohol 3 is allyl alcohol polyether polyol, polyhydric alcohol 4 is vegetable oil polyether polyol, polyhydric alcohol 5 is oxirane end capped epoxypropane polyether polyol, and isocyanate is diphenylmethane diisocyanate. The polyurethane foam has ultralow surface hardness, extremely good supporting performance, the high press-to-sink ratio, and hydrophilia insensitive to temperature changes.