A novel three dimensional LTCC (Low Temperature Co-fired Ceramics) based microreactor with immobilized enzyme (urease) is presented in this paper. The microreactor consists of two chambers separated by a threshold. The shape of the chambers was optimized by the Finite Elements Method. The modeling has brought a better understanding of the microflow of chemically modified glass or polymeric beads through the microreactor. The modeling results are verified by the observation of the fluid movement inside the real structure via a top transparent polymer layer. Moreover, immobilization techniques of enzymes on polymeric beads are investigated. Finally, the properties of the LTCC microreactor are compared with the properties of a similar one made in silicon.