Abstract: In second quantization formalism, finite-N truncation is applied in solving one-dimensional infinite square well problem. The results show that square of the well width parameter a2 is proportional to the truncation parameter N. When N is large enougn（ N ≥ 1 000） , results from the finite-N truncation, at least for low-lying states, are in good agreement to those of exact solution.

Key words: Infinite square well, second quantization, finite-N truncation