In order to analyze effects of main parameters in shale reservoir evaluation， it is necessary to analyze mechanism of these parameters. Investigated are the research progresses in this issue at home and abroad， referred are shale gas exploration and development in five basins of America and analyzed are effects of such parameters as total content of organic carbon， gas content， temperature and pressure on shale gas reservoir evaluation and development. It is found that shale gas reservoir evaluation is more complex than conventional reservoirs， a number of evaluation parameters have both positive and negative effects on the reservoir. The nature of the evaluated reservoir can not be determined by using any single parameter. Shale reservoir contains adsorption gas， free gas and dissolved gas， its adsorption and desorption effects make its percolation behaviors different from any conventional ones. As a result， favorable area preferential selection of shale reservoirs requires comprehensive consideration of various evaluation parameters.