Provided is a method of preparing a high silicon steel thin strip with powder warm rolling. Reduced Fe powder and high purity silicon iron powder with 50%-70% of Si are adopted to form mixed powder with 4.5-6.7% of Si; and a powder warm-rolling slab is sintered in vacuum or reduction atmosphere protection at 1050 DEG C-1150DEG C, so that the Fe powder particles are incompletely sintered, and Si and Fe are partially alloyed to form a porous and incompletely alloyed high silicon steel billet with compressibility. After following multiple times of cold rolling and incomplete sintering, the homogeneous alloying of high silicon steel is realized with the help of thermal diffusion by vacuum or reduction atmosphere protection sintering at a temperature range from 1255 DEG C to 1330 DEG C and thehigh silicon steel strip is obtained, wherein the Si content is 4.5-6.7%, the thickness is 0.1mm to 0.5mm, and the density is 7.34 g/cm3 to 7.44 g/cm3.