Suppose an orientation preserving action of a finite group G on the closed surface Σg of genus g > 1 extends over the 3-torus T 3 for some embedding Σg ⊂ T 3 . Then |G| ≤ 12(g − 1), and this upper bound 12(g − 1) can be achieved for g = n 2 + 1, 3n 2 + 1, 2n 3 + 1, 4n 3 + 1, 8n 3 + 1, n ∈ Z+. Those surfaces in T 3 realizing the maximum symmetries can be either unknotted or knotted. Similar problems in non-orientable category is also discussed.Connection with minimal surfaces in T 3 is addressed and when the maximum symmetric surfaces above can be realized by minimal surfaces is identified.