Abstract: Drying grain or other food is conducive to transportation, storage and subsequent processing, and temperature control is the most important in drying process. The Siemens S7-200 SMART programmable logic controller（PLC） was employed for program design, and Kunlun touch screen was used to realize human-computer interaction, in order to compare the differences of different algorithms in temperature control. At the same time, in order to achieve the purpose of improving temperature control accuracy, the fuzzy proportion-integration-derivative（PID） compound control algorithm and fuzzy PID switching control algorithm were designed by improving the traditional PID control algorithm and fuzzy control algorithm. Ladder diagram language was used to program the above-mentioned four control algorithms and the experiment verification of PLC controlled food drying box was carried out. Results showed that the newly designed fuzzy PID compound control algorithm and fuzzy PID switching control algorithm both reflected the advantages of their combined elements to a certain extent and could effectively overcome the disadvantages of poor dynamic characteristics of traditional PID control algorithm and poor steady-state characteristics of fuzzy control algorithm. When the temperature raised from 30 ℃ to 72 ℃, the fuzzy PID compound control algorithm could shorten the adjustment time by 6 s and reduce the steady-state error by 0.1 ℃compared with the fuzzy PID switching control algorithm.