Abstract: This paper investigates the sum rate optimization in uplink communication for cell-free massive multiple-input multiple-output (mMIMO) systems based on orthogonal time frequency space (OTFS) modulation. An ant colony recursive search mechanism is proposed, which firstly uses the minimum cut grouping algorithm to achieve user grouping, followed by recursive optimization using the ant colony algorithm. Simulation results show that by implementing this mechanism for uplink power control, the better performance is achieved compared to mMIMO-OTFS based on ungrouped and mMIMO-orthogonal frequency division multiplexing (OFDM) systems. Finally, the impact of mobile speed on the performance of the user uplink achievable rate of the system is studied, which shows that the performance gap between mMIMO-OTFS and mMIMO-OFDM system increases with mobile speed.