The main purpose of this paper is to discuss the necessary magnetic & thermal properties of refrigerants and to investigate the magretic cycles suitable for different temperature range. Firstly, the paper shows the calculation results of the magnetic entropy of ferromagnetic and paramagnetic material which is a function of temperature and applied field; secondly, the lattice entropy changed with the Debye temperature is given also. On the basis of etropy analysis, the selection principle of cycle and refrigerant for magnetic refrigeration is provided. And then, the results of recent investigations on magnetic refrigerants are sumed up, these refrigerants can be divided into three groups, one for the Carnot type magnetic refrigerator below 20 K, one for the Ericsson type refrigeration between 77 to 20 K and another one for the refrigerator near room temperature, Finally, the paper points out that high efficient refrigerant and regenerator is the key to achieve the magnetic refrigeration near room temperature.