Being a new two-dimensional layered compounds, the tunable indirect-direct band transformation of BiOCl with different layers can be realized by introducing the biaxial tensile or compressive strains. The band structure and stability of BiOCl with different layers are first researched to clarify the influence of layer numbers. A phase transformation of bilayer BiOCl and metallic characteristic for all are observed under large tensile and compressive strains, respectively. In addition, bond length, interlayer spacing, and band decomposed charge density are calculated to analyze the mechanism behind these phenomena. The results indicate that the band structure transformation is primarily related to the competitions between two kinds of intralayer and interlayer Bi-O bonds and hybridizations between atoms under strains.