The nonlinear Schr dinger equation, which describes the propagation of electromagnetic waves in metamaterials (MMs), are studied by the Hirota method, and two exact spatially-chirped dark solitons, called Dark Soliton I (DSI) and Dark Soliton II (DSII), are obtained under the balance of linear gain and nonlinear absorption. Based on the Drude model, the formation conditions, the existence regions and the transmission characteristics of DSI and DSII in the nonlinear MMs with different electric and/or magnetic polarizations are investigated, and the analytical results are numerically verified as well. It is found that the speed of DSI existing in the negative refraction region gradually increases while the speed of DSII existing in the positive refraction region gradually decreases during the transmission. DSI has a positive chirp, while DSII has a negative chirp. In addition, the beam width of DSII is much smaller than that of DSI. Their background amplitudes and full widths at half maximum are determined by the model parameters, related to the incident wave frequency. Moreover, the transmission characteristics of DSI and DSII are quite different when the MMs are with different nonlinear polarizations. The obtained results indicate that the transmission properties of the chirped dark solitons can be controlled by selecting different nonlinear MMs or different incident wave frequencies.