Baseball has gained popularity at Taiwanese colleges over the last twenty years. The quality of coaching and training is the key factor in the performance of young players during competition. Wireless sensor network (WSN) technology has been developed to index, navigate, store, and analyze data in sports. We investigated the correlations between the performance of college baseball players during a competition game and the following three factors: (1) athletes’ physical fitness, (2) athletes’ psychological state, and (3) the training environment. Wireless wearable devices were applied in this research to construct the indicators for monitoring the development of players in terms of the three aforementioned factors during routine training. The statistics software SPSS 20.0 was employed to test the correlations between the factors raised in this present research. The findings showed (1) correlations among the physical fitness, psychological state, and training environment and (2) correlations between the effect of training on the competition event performance of baseball players during a competition event and the physical fitness, psychological state, and training environment. In the future, the above indicators can be applied to wearable sensing devices to enhance the effect of training on the performance of the players.