We define the Hopf superalgebra UT (sl(1|1)), which is a variant of the quantum supergroup Uq(sl(1|1)), and its representations V ⊗n 1 for n > 0. We construct families of DG algebras A, B and Rn, and consider the DG categories DGP (A), DGP (B) and DGP (Rn), which are full DG subcategories of the categories of DG A-, Band Rn-modules generated by certain distinguished projective modules. Their 0th homology categories HP (A), HP (B), and HP (Rn) are triangulated and give algebraic formulations of the contact categories of an annulus, a twice punctured disk, and an n times punctured disk. Their Grothendieck groups are isomorphic to UT (sl(1|1)), UT (sl(1|1)) ⊗ Z UT (sl(1|1)) and V ⊗n 1 , respectively. We categorify the multiplication and comultiplication on UT (sl(1|1)) to a bifunctor HP (A) × HP (A) → HP (A) and a functor HP (A) → HP (B), respectively. The UT (sl(1|1))-action on V ⊗n 1 is lifted to a bifunctor HP (A) × HP (Rn) → HP (Rn).1 2 YIN TIANand Rouquier [5] categorified locally finite sl 2 -representations, and more generally, Rouquier [32] constructed a 2-category associated with a Kac-Moody algebra. For the quantum groups themselves, Lauda [22] gave a diagrammatic categorification of U q (sl 2 ) and general cases are given by 20,21]. The program of categorifying Witten-Reshetikhin-Turaev invariants was brought to fruition by Webster [37,38] using the diagrammatic approach.On the other hand, the Alexander polynomial is categorified by knot Floer homology, defined independently by Ozsváth-Szabó [27] and Rasmussen [29]. Although its initial definition was through Lagrangian Floer homology, knot Floer homology admits a completely combinatorial description by . It is natural to ask whether there is a categorical program for U q (sl(1|1)) which is analogous to that of U q (sl 2 ) and which recovers knot Floer homology. This paper presents another step towards such a categorical program. We first define the Hopf superalgebra U T (sl(1|1)) as a variant of U q (sl(1|1)) and the representations V ⊗n 1 of U T (sl(1|1)). Then we categorify the multiplication and comultiplication on U T (sl(1|1)), and its representations V ⊗n 1 . In a subsequent paper [36], we will categorify the action of the braid group on V ⊗n 1 which is induced by the R-matrix structure of U T (sl(1|1)).Our motivation is from the contact category introduced by Honda [8] which presents an algebraic way to study 3-dimensional contact topology. The contact category is closely related to bordered Heegaard Floer homology defined by Lipshitz, Ozsváth and Thurston [23]. See Section 1.3 for more detail on the contact category. Motivated by the strands algebra in bordered Heegaard Floer homology, Khovanov in [18] categorified the positive part of U q (gl(1|2)). A counterpart of our construction in Lie theory is developed by Sartori in [33] using subquotient categories of O(gl n ).