Abstract: Perturbation calculation can be used to estimate the changes of effective multiplication factor caused by perturbed system parameters, and is the fundamental of reactor sensitivity and uncertainty analysis.With the development of computer techniques and the increasing needs of new concept and complex reactoranalysis, Monte Carlo perturbation calculation is being used more and more widely. Traditional Monte Carlo perturbation calculation methods, which are limited to low-order perturbation and not considering of perturbed source effects, could cause large errors in perturbation calculations. To overcome the shortages of traditional methods, the high-order differential operator method with perturbed source effects is research in this paper, and this method is implemented in the code RMC. Numerical tests show that the perturbed source effects are very important in perturbation calculation, and large errors will be caused if the perturbed source effects are not considered in the calculation. Also, from the results, we can notice, with higher order, the perturbation results are more accurate.