The general theory of sequential weighted test，and the truncated SPOT is discussed in this paper. The upper bound of the two kinds of error for testing hypothesis of the truncated SPOT is derived. Two application examples of this method are provided：one is the reliability testing of product；the other is the accuracy detecting of the random fall point of the re-entry vehicle. By virtue of using prior information before testing，we can efficiently test statistical hypothesis under the condition of small testing number. This SPOT method is quite significant to statistica1 detection of expensive products.