AZ31B Mg alloy and 6061 Al alloy are joined using low-temperature soldering with Sn-30Zn-xCe solder alloy. The effect of Ce content in Sn-30Zn-xCe solders on microstructure evolution and mechanical properties of the different brazed joints are investigated. The experimental results show that adding appropriate amount of Ce into Sn-30Zn solder is conducive to decreasing the amount of Mg2Sn intermetallic compounds and increasing the amount of Al-Sn-Zn solid solutions in the soldering zone of the brazed joint, which restricts the drawback of the formation of hard and brittle Mg2Sn intermetallic compounds and enhances the mechanical property of soldered joint. The average shear strength of the Mg/Sn-30Zn-0.05Ce/Al-brazed joint can reach 77.48 MPa. Results also indicate that the excessive content of Ce leads to the formation of some Ce-Zn and Ce-Sn intermetallic compounds in soldering zone and subsequently decreases the strength of soldered joint.