Abstract: Positron emission tomography (PET)has been widely used to visualize,localize and quantify the different biochemical processes and parameters such as metabolic processes and receptor densities using anatomical modality.The development of PET technique is to depend on the development and application of positron emitting tracers.The PET radiotracers labelled with positron emitting radionuclides such as ¹⁸F,¹⁵O,¹³N and ¹¹C are commonly produced in cyclotron.Therefore,it is very important to master the operational principles and the essential component of the cyclotron,and to select the suitable positron emitting radionuclides and corresponding la belling precursors for the routine production and development of PET imaging agents.This review described the principle of operation of the cyclotron,types of medical cyclotrons,production of radionuclides and labelling precursors.