The aim of this study is to develop a new kind of radiation dosimeter based on diamond films, which could overcome the shortages extensively existing in traditional ones, such as low sensitivity and spatial resolution, poor radiation hardness as well as short endurance, etc. The effort of this paper may have great significance for the research in those fields just like radiation medicine, space irradiation, reactive plant and accelerator, etc.In this investigation, the preparing procedures and electrical properties of diamond films with high phase-purity and high-degree preferential orientation were studied systematically using a bell-jar type MWPCVD (microwave plasma assisted chemical vapor deposition) setup. Then, as-deposited films were treated by a new technique named in-situ Oxygen plasma etching processing. After post-deposition treatment, they were made into photoconductive type radiation dosimeters with sandwich structure, whose features were taken a preliminary characterization utilizing a steady-state x-ray source. Finally, the relationship between the phase-purity and structure of diamond films and the performances of as-prepared dosimeters was researched and analyzed.In order to obtain diamond thin films with high purity and high-degree orientation, a new preparing technique had been designed out and made a optimum. In its researching course, it was found that the CH4 concentration in reactive gas greatly influence the phase purity and grain orientation of deposited films. When it changed from 0.21% (Vol.%) to 0.28% and then to 0.35%, the preferential orientation varied from [111] to [110] followed to [100] correspondingly, while the containment of non-diamond phase increased gradually at the same time. Amongthese films, the [100] oriented has the most regularly grain array and the highest-degree orientation, along with the most of non-diamond content. The microwave/substrate temperature parameters also have obvious effect on the phase purity. To further improve the film composition under the condition of no big alteration in grain orientation, two special procedures namely nucleation-etching-growth and growth-etching-growth æ™»? circulating deposition techniques were developed, which was characterized with its simplification and practicability. Using this technique, [100] textural film with high purity and high-degree orientation had been successfully deposited, whose resistivities is in the range of 1014 order magnitude, reaching the national advanced level among the same oriented films.For the first time, a simple convenient in-situ Oxygen plasma etching method had also been explored to make a post-treatment for deposited films. Micro-characterization and electrical measurement demonstrated that, under the condition of no remarkable variation in film thickness, the non-diamond phase composition in the surface layer of the films could be reduced significantly which resulted in effective enhancement in film resistivities (the most value being enlarged about four order magnitude).The resistivity testing results of post-treated diamond films also showed that, for [100] preferentially oriented ones with the most of non-diamond phase content, they had the lowest resistivities while for [111] with the highest purity, their resistivities were the largest; but if the [100] oriented films were synthesized by growth-etching-growth-" rotation deposition technology, their resistivities could be enhanced by two order magnitude, and also be very close to that of [111] oriented ones" .Dosimeters with simple Au / Diamond film / Si sandwich structure were made from post-treated diamond thin films, and were examined with steady-state X-ray source. Under 8 kV / cm bias field, their photo-current output was easily observed and was also proportional with the flux intensity of incident X-ray.