The studies of the main characterestics of the maser-instability driven by elec trons with a losscone-beam distribution are carried out on the basis of the the oretical model of Chen et al (2002, Phys. Plasmas 9,2816; 2003, Acta Phys. S in.52,421). This kind of electrons may be created by the reconnection near the chromosphere of the sun. The electrons have the characters of both losscone and beam. The results show that it can excite the fundamental and harmonic radiatio n of extraordinary and ordinary modes in an appropriate region of plasma freque ncy over the gyrofrequency with the characters of both losscone and beam distri bution, and with much stronger growth rate. It enriches the fundamental content of the plasma instabilities. It is expected to be applicable widely in the stud y of solar and celestial emission mechanism.