The entanglement dynamic properties between two mechanical modes and nitrogen-vacancy(NV) centers in the system of second-order-magnetic-gradient induced nanodiamond NV center coupled to mechanical resonator are investigated. The influences of coherence angle, decay rate of mechanical modes and spontaneous decay rate of NV centers on entanglement are analyzed. The research results show that the maximum entangled state between mechanical modes and NV centers can be produced by the suitable choice of system parameters. In addition, the coherence angle has an important influence on the entanglement dynamics, and the coherence angle can be used to effectively adjust the resistance ability to entanglement attenuation when dissipation is considered. Moreover, compared to the spontaneous decay of NV centers, that of mechanical modes can make the system entanglement decay and disappear more quickly.