Compressively strained BiFeO3 (BFO) films from 19 to 114 nm are epitaxially grown on LaAlO3 substrates, and their thickness-dependent evolutions of structural and magnetic properties are investigated. Across the morphotropic phase boundary, complex strain relaxation behaviors involving low-symmetry intermediate/bridging phases are observed. The fully strained 38 nm BFO film exhibits a saturation magnetization of ∼ 28 emu/cm3 at 300 K with a coercivity of 130 Oe while all films show a spin-glass behavior. These findings suggest that tailoring film thickness is effective to suppress the cycloidal magnetic modulation in BFO, leading to magnetic properties different from the bulk counterpart.