A computer-implemented method of executing an instruction sequence with a recursive function call of a plurality of threads within a thread group in a Single-Instruction-Multiple-Threads (SIMT) system is provided. Each thread is provided with a function call counter (FCC), an active mask, an execution mask and a per-thread program counter (PTPC). The instruction sequence with the recursive function call is executed by the threads in the thread group according to a program counter (PC) indicating a target. Upon executing the recursive function call, for each thread, the active mask is set according to the PTPC and the target indicated by the PC, the FCC is determined when entering or returning from the recursive function call, the execution mask is determined according to the FCC and the active mask. It is determined whether an execution result of the recursive function call takes effects according to the execution mask.