Sphere-surface distance and exposure dose effects on lithography resolution of microsphere lens array are studied. A transparent gap is introduced between photoresist film and polystyrene microspheres to adjust light distribution of photoresist surface. The pores size on the photoresist film varies when the gap thickness is changed. By optimization gap thickness and exposure dose, sub-100 nm surface patterning array is achieved for sphere of 2.06 µm diameter and optical wavelength λ of 400 nm theoretically and experimentally. Furthermore, when smaller polystyrene sphere (1.25 µm diameter) is chosen, spot width of 35 nm is realized by numerical calculation. This nano-fabrication method is simple, low-cost and high-efficiency, which can provide opportunities to make a variety of nano-devices, such as biosensors and nano-antennas.