Abstract: Crop straw can be used as clean fuel, rapid detection of the fuel properties for straw energy utilization has important significance. This paper through studying the content and calorific value correlation between cellulose, hemicellulose and lignin in the straw samples, found that lignin and hemicellulose two ingredients as the main energy indexes determine calorific value of straw. The results of variance analysis of each ingredient content of wheat and rice straw showed that: ash content, N, P, Na, and Mg contents in rice straw were significantly higher than those in wheat straw (P<0.01); the calorific value and the contents of volatile, fixed carbon, cellulose, hemicellulose, lignin, C and H in rice straw were significantly lower than those in the wheat straw(P<0.01); the difference of moisture, K, Ca, and Fe contents in rice and wheat straw was not significant(P>0.05). Based on the C, H, N contents in straw, established multiple linear model to predict the thermal value of the sample, the Correlation Coefficient of Determination (R2) of the predicted value and the true value reached 0.9273, root mean square error of 224 J/g.