Abstract: As the most direct method of obtaining the underground information from the earth, continental scientific drilling involves continuous coring and testing in the deep wells, so as to study the composition and structure of the earth, and the evolving process of underground bio-circle and water circle. Combined with the pre-research programs of China Continental Scientific Drilling (CCSD), this paper investigated the technical difficulties of designing the downhole instruments, and analyzed the testing circumstances of such parameters as hole inclination, temperature and pressure, etc., as well as the significance of conducting these testings. Using the method of Measuring While Drilling (MWD) and the testing means of storing the information in the down-hole and playing back on the surface, the primary designs such as its principle, structure and electric circuit have been finished; meanwhile the sample instrument named DPMA-1 has also been made. Field test indicated that this downhole testing systems can adapt such difficult conditions as high temperature, high pressure, vibration and obtain the continuous parameters of the drilling trajectory. DPMA-1 can also be used to monitor the changes in the temperature and pressure of drilling fluid, so as help to judge the working condition of the downhole motor, and drilling fluid circulation resistance, etc. Thus measurement while drilling can be realized and assistant operation time was cut down dramatically.