During the implementation of the SLAM methods based on probability hypothesis density (PHD) with sequential Monte Carlo (SMC), it is necessary to generate a relatively large number of particles for mapping and cluster particles for target state extraction, which brings about heavy computing requirements and difficulty in enhancing the estimation accuracy. Along these lines, in this work, an interval SLAM algorithm for Leg-Arm mobile robot (LA-MR) was presented, which was based on cardinality-balanced multi-target multi-Bernoulli filter with Gaussian indicator box-particle (GIBP-CBMeMBer). First, an effective strategy for improving the selection criterion of subdivision box-particle was given via the indicator subdivision resampling (ISD-resampling) to provide more reliable box-particles. In addition, mixtures of Gauss distributions with box supports were developed to fit posterior probability, i.e. Gaussian indicator box-particle (GIBP). Then, the GIBP filter was employed to implement cardinality balanced multi-target multi-Bernoulli (CBMeMBer) filter and thus the particle numbers were significantly reduced to decrease the computational complexity compared with the SMC-CBMeMBer filter. In this way, the feature map learning was considered as a multi-target tracking problem, whereas a kind of SLAM algorithm for LA-MR was also designed and implemented through the GIBP-CBMeMBer filter, in which the GIBP filter was used to realize simultaneous localization and the GIBP-CBMeMBer filter was utilized to build a map. A series of experiments and a case study clearly illustrated the performance superiority of the proposed algorithms.