In order to ensure the timeliness and reliability of power line carrier communication, a grouping adaptive MIMO-OFDM modulation method based on the requirements of service delay and bit error rate was proposed.Firstly, the power line communication service is divided into real-time(RT) service and non-real-time(NRT) service from the perspective of timeliness. Then, from the perspective of reliability, the business is divided into high-level business and low-level business. On this basis, the grouping strategy and modulation mode are selected adaptively. The simulation results show that the computation iteration times of this method is less than that of the no-grouping algorithm.By comparing the grouping algorithm, the extra service delay caused by grouping is avoided and the sub-carrier loading efficiency is improved.