With the explosion of population and the rapid development of technology and economy, human activities have been a greater and greater effect on the earth. Human unreasonable activities have led to the degradation of ecology and aggravated the occurrence of natural disasters. Therefore, the effects of human activity on ecology and environment have been one of the key points in the study of man-land relationship. This paper firstly reviewed and discussed the deep impact of human activities on ecology and environment. The main impact types include: land use, large-scale engineering constructions, urban expansion and inducing natural disasters. The main impact approaches: land cover change, habitat and species loss, speeding up surface sediment transfer, increasing energy inputted into nature, and new substances (pollutants) generated and transfered in natural environment. The impact is multi-time scale, from day, month, year, century to geological ages and is also multi-space scale, from local, landscape, regional to global sphere. Second, the authors emphasized the importance of exerting the positive role of human activities and carrying out the regional ecological reconstruction in China. Third, in order to evaluate quantitatively human activity intensity and seek the methods to regulate the direction and velocity of human activity, the authors enumerated and commented on some human activity intensity and critical point regulation indexes which are respectively Economic density, Population density index, Human action relative intensity, Ecological footprint, Human activity index, Disturbance degree index, Human effect intensity model, Renewable resource use threshold, Environmental Kuznts Curve, Net primary productivity, and Biodiversity safety threshold. Fourth, the authors brought forward briefly the principles for regulating human activities. At the end of this paper,the authors expressed a preliminary idea on the theory of landscape ecological reconstruction focusing on orderly human activity,which should be a useful theory for evaluating and regulating human activities actively.