Abstract: In this paper, we address the problem of constructing a Steiner tree in the Euclidean plane $\mathbb{R}^2$ using stock pieces of materials with fixed length, which is modelled as follows. Given a set X = {r₁,r₂, …,r_n} of n terminals in $\mathbb{R}^2$ and some stock pieces of materials with fixed length L, we are asked to construct a Steiner tree T interconnecting all terminals in X, and each edge in T must be constructed by a part of that stock piece of material. The objective is to minimize the cost of constructing such a Steiner tree T, where the cost includes three components, (1) The cost of Steiner points needed in T; (2) The construction cost of constructing all edges in T and (3) The cost of stock pieces of such materials used to construct all edges in T. We can obtain two main results. (1) Using techniques of constructing a Euclidean minimum spanning tree on the set X and a strategy of solving the bin-packing problem, we present a simple 4-approximation algorithm in time O(nlogn) to solve this new problem; (2) Using techniques of computational geometry to solve two nonlinear mathematical programming to obtain a key Lemma 8 and using other strategy of solving the binpacking problem, we design a 3-approximation algorithm in time O(n³) to resolve this new problem.

Key words: Combinatorial optimization, Euclidean plane, Steiner tree, Stock pieces of materials with fixed length, Approximation algorithms