For insurance company, claims service time is an important index of claims service quality. It has a biggish impact on other indicators and business promotion of insurance, and the image of insurance company. According to the date of insurance claims service quality indicators in some provinces and cities in China, this paper analyzes insurance claims service time distribution function. And under the discussion of distribution types and characteristics, we have a research on practical bounds in an uncertain condition of distribution function. On the basis of this study, we discuss the solution of insurance claims time distribution and bounds through two examples. Then we can get the specific distribution of outstanding loss reserve required.