In order to improve the properties of Co—Ni—Ga alloys, experiments of adding Si to Co50Ni21Ga29 alloys were carried out to examine the effect of Si in quaternary Co50Ni21Ga29Six (x=1—2) alloys on their structure, martensitic transformation behavior and magnetic properties. The Co50Ni21Ga29Six (x=1,2) single crystals were successfully grown. All the samples with low Si doping show a sharp martensitic transformation with increasing temperature. The single crystal samples show a completely recoverable two-way shape memory with a strain of 2.5% upon the thermoelastic martensitic transformation. A large magnetic-field-induced strain of 110 ppm was measured at room temperature. A small quantity of Si doping can down-shift the martensitic transformation temperature, reduce the thermal hysteresis, decrease the magnetization but increase the Curie temperature. Especially, the Si doping can increase the magnetic anisotropy of Co—Ni—Ga-alloys, which is available to obtain large magnetic-field-induced strain in a low magnetic field. An electronic resistance “jump" of 4.5% upon the thermoelastic martensitic transformation was also reported.