In this paper we mainly investigate, in the framework of effective mass bag model, how the coupling constant and the bag constant execute their effects on equations of state of strange quark matter, and on the properties of strange stars. Numerical results indicate that with the increase of strong coupling constant and bag constant, equations of state for strange quark matter turn softened, whereas gravitational mass and corresponding radius of strange stars become decreased. For instance the mass of the star decreases from 1.43M⊙(M⊙=1.991030 kg)to 1.25M⊙ and corresponding radius decreases from 8.3 km to 7.7 km while the coupling constant varies from 0.5 to 2.0. As for strange stars, the corresponding values decrease from 1.47M⊙to 1.22M⊙ and 8.6 km and 7.4 km respectively while the bag constant B1/4 increases from 160 MeV to 175 MeV.