The invention provides a moderate-temperature brazing filler metal for graphite-base composite material connection and a preparation method thereof, and relates to a moderate-temperature brazing filler metal and a preparation method thereof. The moderate-temperature brazing filler metal is used for solving the problems that the existing graphite-base composite material is poor in low temperature brazing effect. The moderate-temperature brazing filler metal comprises the following ingredients in parts by weight: 48-53 parts of Ag, 19-32 parts of Cu, 10-28 parts of Sn and 0.1-7 parts of Ti. The method comprises the following steps of 1, weighting all the ingredients, putting the ingredients into a graphite crucible at a ball-to-ingredient mass ratio of (12-16):1, and performing ball milling for 2-6 hours at room temperature and the rotation rate of 280-320r/min (revolutions per minute) in the presence of argon, so as to obtain mixed powder; and 2, pressurizing the mixed powder for 6-10t to obtain foil, performing ultrasonic cleaning on the foil, and drying the foil at room temperature, so as to obtain the moderate-temperature brazing filler metal. The shearing strength of a Gr/2024Al composite and a metal solder joint obtained in the invention at room temperature is up to 20MPa. The moderate-temperature brazing filler metal provided by the invention can be applied to the field of aerospace.