in what condion coulombs law is applicable?is this law applicable in case of two charges are moving under attraction .

coulomb's law is applicable only when both the charges are at rest

No, coulomb's law is valid if the charges are or are not moving. If both the charges are moving, the force varies but the law is still valid. You can say that for time t, the charges are at a separation r and at time t+dt, the separation increases to r+dr or reduces to r+dr(dr being negative).