The Monte-Carlo algorithm is an effective method to study the Curie temperature of a ferromagnetic system related to its exchange constant, magnetic moment, and co-ordination number. Curie temperatures of the three types of ferromagnetic systems are calculated, e.g., the hexagonal crystal system, the tetragonal sys-tem, and the orthorhombic system. In order to make the calculated magnetic moment-temperature curve fit a steep slope, the size of the supercell of the ferro-magnetic system is selected as small as possible, and Monte-Carlo steps are per-formed 5000000 times at each temperature. The calculation reveals a significant result: the Curie temperature scales with the exchange constant and the square of the magnetic moment.

Curie temperature is an important parameter in the second-order thermodynamic phase transition of a magnetic system. However, the classical Heisenberg?s mean field theory tends to overestimate heavily the temperature. In order to solve this problem, firstly, the structure of ferromagnetic and spin-glassy materials in a magnetic system is established by the Ising model. Secondly, the respective energy of ferromagnetic and spin glass states is calculated by Monte Carlo method. Finally, Curie temperature is predicted through the obtained energy, which agrees well with experimental data. A new strategy to estimate accurately Curie temperature is presented.