Abstract: The uncertainty analysis is a key link in activation neutron spectrum measurement. According to SAND-Ⅱ activation neutron spectrum unfolding process, an uncertainty analysis Monte-Carlo method of neutron spectrum measurement based on cross-section covariance, activation rate and prior spectrum information was presented. First, the sampling method of cross-section covariance based on linear transformation was built. Then, the error was computed with MCNP, and the uncertainty of prior spectrum was obtained using iteration method. Finally, combining uncertainty of activation rate measurement, the neutron spectrum uncertainty using Monte-Carlo sampling algorithm was calculated. In the verification of this method with ²⁵²Cf spontaneous fission spectrum, its uncertainty analysis result was more comprehensive than that of traditional method. The uncertainty analysis of a neutron spectrum measurement for Xi’an Pulsed Reactor was analyzed. The analysis result shows that the method is more conservative.