The invention relates to Joining system for floor panels (1). The floor panels (1) are provided with coupling parts (20) on at least two opposite sides (30, 40) for joining floor panels (1) together. The coupling parts (20) include a groove (50) and a tongue (60), where the groove (50) is shaped for insertion of a tongue (60) on an adjoining floor panel (1). The tongue (60) is shaped for It locking engagement by means of integrated locking means (70) with the groove (50) in a direction perpendicular to said sides (30, 40) and parallel to a horizontal floor plane (FP) defined by the joined panels (1). The invention is especially characterized in that: - the locking means (70) comprises dual consecutive locking recesses (80, 90) arranged in a lower portion (95) of the groove (50), a first locking recess (80) of which being located in an internally extending portion (100) within the groove (50) and a second locking recess (90) of which being located in a lip portion (110) protruding from an entrance opening (120) of the groove (50), the locking means (70) further comprises dual consecutive locking lugs (130, 140) arranged in a lower portion (150) of the tongue (60) for horizontally interlocking engagement with said dual consecutive locking recesses (80, 90) in the groove (50), a first locking lug (130) of which extending downwardly from a lower tip portion (160) of the tongue (60) and a second locking lug (140) of which extending downwardly from a root portion (170) of the tongue (60), wherein the first locking recess (80) and the first locking lug (130) are provided with matching curved horizontal locking surfaces (180, 190) and wherein the second locking recess (90) and the second locking lug (140) are provided with matching inclined horizontal locking surfaces (200, 210).