Amorphousized Ni30Co10RE60 (RE = Ho and Tm) ribbons have been prepared by melt-spinning technique, and their microstructure, glass formation ability, magnetic properties and cryogenic magneto-caloric effect (MCE) were systematically investigated. Based on the X-ray diffraction and high-resolution transmission electron microscopic, the Ni30Co10Ho60 and Ni30Co10Tm60 ribbons show fully amorphous structure. The ribbons are confirmed to reveal a second-order magnetic phase transition (paramagnetic to ferromagnetic) by the magnetization measurements and Arrott plot analysis. A considerable MCE is found in Ni30Co10Ho60 and Ni30Co10Tm60 ribbons around their respective Curie temperatures (T (C)) of 22.7 and 6.3 K, respectively. Under a magnetic field change (a dagger H) of 0-5 T, the magnetic entropy change (- a dagger S (M)) reaches 12.5 and 14.2 J/kg K, and the relative cooling power reaches 447 and 242 J/kg for Ni30Co10Ho60 and Ni30Co10Tm60, respectively.