A spring mattress structure comprises a mattress body with a top bed surface and a bottom bed surface developed by a plurality of shaft levers which are regularly arranged and separated by a spacing: each of the shaft levers on which a plurality of springs are installed allows each spring's two bottom ends to be positioned at two adjacent springs; each of the springs has a hollow space corresponding to the spacing developed by two adjacent shaft levers and makes its bottom fixed on a shaft lever with a spring-loaded locating piece; the spring-loaded locating piece comprises a locating part on which a shaft lever is fixed; the locating part has elastic fasteners extending from both sides and used to clamp spring coils of springs so that the springs are stably connected to shaft levers.