In the paper, in order to investigate the situation of impact on wet molding for straw of compressing speed and moisture ratio, and look for the inside law between them, closed compress experimental study on the wet molding for wheat straw pellet fuel was done by electrical universal material experimental machine and experimental provision made by oneself. Study on the impact situation for compressing speed and moisture ratio was done from pressure intensity, displacement and density of materiel. The result, which low compressing speed and low moisture ratio were propitious to wet molding, was gotten. The molding stage can be divided to loose stag, transitional stage, compressing stage. Partial elastic deformation mainly occurred In loose stage, and its mathematical model was linear equation. Elastic deformation mainly occurred In transitional stage, and its mathematical model was exponential equation. Plastic deformation mainly occurred In compressing stage, and its mathematical model was linear equation. The conclusion above has general directive significance to wet molding for straw pellet fuel.