In the process of the transition from urban and rural dual economy to unified economy of urban and rural integration, the concealed unemployed surplus labors of urban and rural areas of China become migrant workers. Thus, in order to know and master the total unemployment rate of China, the key is to know the scale of urban and rural surplus labors in transitional period in these years. This paper examines the concealed unemployment (surplus labors) from the perspective of population flowing and the total unemployment of China and uses DEA (data envelopment analysis) to estimate the total unemployment rate of China from 1978 to 2007. The results show that the total unemployment rate of China in the 30 years is 6 percent to 10 percent and that the relationship between unemployment and growth is consistent with Okun Law. The first envelopment line is the maximum supply curve of surplus labors and this curve envelops the peak value of all flowing labors. The second envelopment line is supply curve of urban constant labors and this curve envelops the lower value of all flowing labors