Microwave heating is a rapid and convenient food-reheating method. However, uneven heating often occurs. To study the 'cold spot' problem of chilled instant rice during microwave reheating, online monitor was used to determine the temperature distribution during reheating. A cylindrical model was used to simulate the microwave reheating process of instant rice, and Lambert's law was applied to analyse the microwave power absorption of rice and to predict the reheating temperature. The results showed that the internal temperature was highest at the geometric centre during microwave reheating. The predicted data using Lambert's law matched the experimental results with relatively good agreement, and the correlation coefficient R2 is between 0.990 and 0.999.