Abstract: An assembled bed mattress includes an upper sheet having a plurality of upper sleeves made as bellows protruding downwardly from the upper sheet, a lower sheet having a plurality of lower sleeves made as bellows protruding upwardly from the lower sheet each lower sleeve being axially aligned with each upper sleeve, a plurality of helical springs each spring jacketed in each upper sleeve and each lower sleeve, and a fastener wire or zipper securing the two sheets to form an integral bed mattress having the plurality of springs resiliently retained between the two sheets, whereby upon a dismantling of the two sheets, any partial damaged springs can be replaced with perfect springs for easier maintenance of a mattress.