The basic optical property and phase-matching of new mixed AgGaGeS4 crystal are presented. Frequency conversion, in particular the SHG of 30ns pulses of 9μm emission band of transversely excited atmospheric-pressure (TEA)CO2 laser, is realized in AgGaGeS4 for the first time. As high as 0.57% peak power and 0.3% exteal energy efficiencies, and 0.7mJ harmonic pulse energy are obtained for the 9.55μm emission line at pump intensity of 4% level of the damage threshold.