Abstract: In this paper, the influence of the solar wind on the retardation of rotation of the sun is examined. The theoretical expressions for the relative variation rate and secular variation of angular velocity of rotation are derived. For the relative variation rate, the effect of mass loss due to solar wind is negligible; but for the secular variation, it can not be neglected The results of numerical computation are given. The relative variation rate(这里有图片19900405-274-1.GIF)/ω= -5.4× 10^-10/year. The curve of secular variation in 10⁷ year is plotted in Fig. 1.