The invention discloses an inference method for carrier rocket redundant substances on the basis of a Bayesian theory. The method comprises the following steps that: (1) establishing a redundant substance model, and carrying out sampling; (2) simplifying the redundant substance model into a black box ball touching model; (3) on the basis of the black box ball touching model, calculating all probable values of black ball numbers, calculating the probability of each probable value according to the Bayesian theorem, obtaining a probability distribution density function of the black ball to serve as the probability distribution density function of a redundant substance amount, and taking the probable values of black ball numbers as an abscissa and the probability corresponding to the probable values of black ball numbers as an ordinate to draw a curve graph; and (4) according to the probability distribution density function of the redundant substance amount, calculating the inference value of the final redundant substance amount, and setting the value interval of the redundant substance amount under a confidence level. Compared with the prior art, the method disclosed by the invention is more reasonable and accurate.