The unascertained mathematics was introduced to analyze the representative values of compressive strength of concrete core from cast in-suit pile at the condition of small sampling data.The compressive strength of 15 sets of concrete core from 5 cast in-suit piles were tested as a practical example,and compared with the results from relative standards.The results show that the(method) is not only applicable in assessing the practical states of compressive strength of concrete pile,but can obtain the confidence level of representative values of compressive strength also.