A temperature tolerant starch composition for well drilling liquid and method of preparing the same, which includes starch, catalyst, cationic reagent and cross linker, wherein starch comprises potato starch, cassava starch, corn starch, with a weight ratio of 30-80:20-60:10-50; weight ratio between catalyst and starch is 5-30:100, weight ratio between cationic reagent and starch is 1-20:100, and weight ratio between cross linker and starch is 0.01-0.6:100. The inventive temperature tolerant starch composition for well drilling liquid not only inhibits yeastiness thereof effectively and enhances tolerant temperature from 120 DEG C to 150 DEG C, so that application range of the starch is widen, but also protects environment because of biodegradability. Moreover, the preparation is simple in process, mild in reaction condition, high in conversion, low in cost, without subsequent process and waste, which makes it economic and environment protective.