This article investigates regression analysis of multivariate current status data with the use of a class of flexible semiparametric transformation frailty models. For the problem, the maximum likelihood estimation procedure is derived and in particular, a novel EM algorithm, which is quite stable and can be easily implemented, is developed. Also the asymptotic properties of the resulting estimators are established and the numerical study indicates that the proposed methodology works well in practical situations. An application is provided for the illustration of the presented method.