In order to compare the effect of different mechanical-chemical coupling treatment on wheat straw and provide guidance for the subsequent preparation of cellulose nanomaterials, this paper systematically explored the impact of different scale mechanical fragmentation coupling various NaOH concentration treatment on the lignocellulosic components, micromorphology and cellulose crystal structure of wheat straw. The results showed that the relationship between hemicellulose and lignin removal with NaOH concentration can be expressed as exponential function Y = a_i(1-exp(-b_iX)), and micro-nano-scale ball-milling coupling NaOH treatment can facilitate the removal of hemicellulose and lignin. Micromorphology analysis found that wet ball milling coupling NaOH one-step treatment can disintegrate cellulose fiber into crosslinked network structure of cellulose microfibrils. XRD results indicated that wet ball milling with NaOH solution was contributed to retaining cellulose crystal structure and conducive to cellulose crystalline transformation. In conclusion, wet ball milling coupling NaOH simultaneous treatment can be a promising pretreatment for cellulose nanomaterials preparation.