Method for preparing semi-aromatic polyamide

The invention discloses a method for preparing semi-aromatic polyamide. The method is characterized by comprising the following steps of: adding 200 to 800 parts of monomer, 1 to 10 parts of catalyst and 50 to 200 parts of deionized water into a reactor, and reacting at the temperature of between 200 and 250 DEG C for 2 to 5 hours; exhausting gas, vacuumizing until the vacuum degree is 0.07 to 0.09MPa, filling inert gas until the vacuum degree is 0.5 to 1.5MPa, reacting at the temperature of between 220 and 280 DEG C for 1 to 2 hours, and repeating gas exhausting, vacuumizing, gas filling and reacting operation for 1 to 4 times; and reducing the temperature, discharging, grinding a solid, washing, drying, adding into a reactive extruder, and performing reactive extrusion at the temperature of between 260 and 320 DEG C and the vacuum degree of 0.07 to 0.09MPa for 1 to 30 minutes to obtain high molecular weight semi-aromatic polyamide resin with the intrinsic viscosity [eta] of 1.0 to 2.5dL.g, the melting p