The invention discloses a switching method and a system of the transmission mode from PTP to PTM. The method comprises the following processing that a RNC judges whether the transmission mode switch from PTP to PTM is necessary in an nth modification cycle and establishes a PTM RB; the RNC sets the action of the UE corresponding to the service to be acquiring the PTMRB information in an n+1th cycle and transmits the PTM RB information to the UE; the RNC transmits the RB release information to the UE; the UE releases the PTP RB and establishes PTM RB according to the PTM RB information transmitted by the RNC. With the invention, the MBMS services could be switched from the transmission mode of PTP to PTM and the process of UE releasing the PTP RB is effectively controlled to establish the PTM RB and receive the MBMS transmitted in the mode of PTM.