In the core of some massive neutron star there may appear pion condensate. The weak processes such as μ(p1)→μ(p2) + e- + ve and μ(p1) + e→μ(p2) + ve (i. e. equation (9) and (10) of this paper), in pion condenate,have been proved to be essential in damping the radial vibrations in the neutron star. The time scale of this damping effect is model depen dent and may be several days.Considering processes (9) and (10), the equilibrium condition in the pion condensate is μπ=μe. However, only irreversible processes could damp the vibration, so the key parameter here should be ξ=(μπ,-μe)/kT describing the deviation from equilibrium. In this paper, we have derived the reaction rates of processes (9) and (10), and the related neutrino luminosities, and done numerical calculations. Results obtained are the relations of W-t and T-t, as shown in Fig. 2 and 3, using Wv and T to denote the vibrational energy and the temperature of the neutron star respectively.