The characteristics of martensitic transformation and magnetostructural coupling have been investigated for MnNiGe1 xGax(x =0—0.30) alloys. It has been found that the martensitic transformation temperature of the system can be deceased about 400 K by doping a low content of Ga to substitute for Ge. Adding Ga may weaken the hybridization and at the same time enhance the magnetic exchange interaction, which are responsible for the increase of the atomic moment and the Curie temperature in the austenitic phase...