Abstract: Technical problems encounered in the preparation of large area free standing thick diamond films are discussed. Cracking of deposited diamond wafers is mainly due to the huge thermal stress resulted from the big difference in linear expansion coefficients between diamond and the Mo substrae. While the status of the surface preparation of the substrate, the control and optimization of process parameters are also very important. In order to obtain crack free large area thick diamond wafers it is necessary to strictly control the every step of the whole deposition process.