By studying the application of sandwich-structured synthetic diamond core bits, following results are concluded: Matrix hardness can be HRC3-5 higher than that of similar ordinary ones; Finer diamond can be used partly as substitute of coarse ones, or even a fraction smaller size can be adopted, which can reduce the cost with better performance especially for drilling medium to hard formation (grade 8-10); Many factors should be considered when designing the width of interlayer, and usually it should be 1/5 to 1/4 that of the kerfs. The problem of short working life of core bit because of wearing out of the inner wear-resistant layer can be solved by adding 5% to 8% RVD2 of 70/80 mesh to strengthen the inner layer or the width of inner layer being 1/3 that of the kerfs. Such experience is beneficial to the manufacturing technology of Sandwich-structured Diamond Core Bits.