Abstract: The blend solutions of poly(L-lactic acid) (PLLA) and wheat straw fiber (WSF) were prepared in the solvent of N-methyl morpholine-N-oxide. Then the blends of PLLA and WSF were also prepared. Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction were performed to determine PLLA/WSF blends. The compatibility and crystalline of PLLA and WSF in blends were investigated. The results show that PLLA and WSF can form a homogeneous mixture solution in N-methyl morpholine-N-oxide. Strong interaction between PLLA and WSF can be detected, which suggests good compatibility between the two components in PLLA/WSF blends. The morphology and properties of PLLA/WSF blends vary with the ratios of PLLA to WSF. With increasing PLLA contents, the glass transition temperatures of PLLA/WSF blends gradually reduce to that of PLLA. Both PLLA and WSF are crystalline, while PLLA/WSF blends are amorphous when the ratio of PLLA to WSF is less than 6:4. When the ratio of PLLA/WSF is more than 6:4, the blend is crystalline and their melting points increase with increasing PLLA contents. Thus biodegradable polymeric materials with different properties can be prepared through changing ratios of PLLA to WSF.