This Paper introduces a temperature detection system in beer fermentation. A temperature monitoring system with characteristics of bus topology structure is composed of industrial computer, temperature detector, bus converter, transmission bus and especially 1-wire digital temperature sensor DS18B20. Four-core cable is used to form a tree-like or star-like network, in which 54 digital temperature sensors existing on 18 fermentation tanks can be connected. The quantity of junction wires between temperature sensor and computer will be reduced greatly. Temperature detector provides power supply for bus converter and DS18B20 through Four-core cable. Because bus converter has used hardware fault detecting technology, the fault temperature sensor can automatically detach from the main bus and will not affect normal working of other sensor in network. So to solve the problem of a certain sensor or branch's damage causing the paralysis of entire bus. The length of detecting temperature bus can reach more than 500 meters. These all make system maintenance and expansion easy. The experiments show that this system is characterized by high intelligence, high-precision, capability of making temperature test on multi-points and compensating function. The method has a good applicable value to the temperature test.