The invention discloses a Monte Carlo method-based cargo packet drop angle analysis method and system. The method comprises the following steps of: step 101, recording random sampling times; 102, generating a random number; 103, performing sampling to obtain each random variable; 104, based on each random variable obtained by sampling at this time, carrying out simulation analysis on a collision accident scene at this time, and determining a cargo packet drop angle simulated at this time as a sampling result at this time; step 105, performing statistical analysis on the sampling result of the current time; and 106, carrying out credibility evaluation on the statistical analysis result, if the evaluation result is credible, ending the evaluation, if the evaluation result is not credible, adding 1 to the sampling times, and returning to the step 102, and continuing to repeatedly sample. According to the method and the system provided by the invention, the cargo packet drop angle in a single collision accident scene is analyzed through a Monte Carlo method, a credible confidence interval is given according to the drop angle, and the result credibility of subsequent accident analysis and radiation risk evaluation is ensured.