Abstract: A high precision and small sample method for calculating composite allowables is given. It can combine the previous data with the current ones to predict the composite allowables. Thus, it has overcome the disadvantages of traditional methods caused by the large scatter of the composite materials, such as a great number of specimens and expensive test. Furthermore, a new method for F test with scaling factor is also put forward to solve the problem of variance coefficient test. Full use is made not only of the standard variance, but also of the variance coefficient. In this paper, the tension, compression, bending and shear experimental data for three kinds of advanced fiber reinforced composite materials have been used to the allowables calculation. It shows that fewer specimens (only about half) are required in this method and the result is more accurate for the same number of specimens by these contrast examples.