The continual growth of public investment in Xinjinag from 1990 to 2007 has effectively promoted the economic development there.However,the ratio of public investment to GDP shows an earlier raised and later decreased tendency and the internal structure of public investment hasn't undergone great changes with public infrastructure accounting for a higher proportion and the ratio of urban public investment bigger than that of the rural areas.The problems of public investment are found in its unclear orientation,unreasonable investment scale and irrational investment structure.Therefore,efforts should be made to increase the investment share in agriculture and rural areas,increase investment in education,science and technology based on the reasonable scale.