In order to investigate the dielectric properties of the different amino acid solutions during microwave heating, the 10 kinds of amino acid solutions [glycine (Gly), proline (Pro), cysteine (Cys), glutamine (Gln), lysine (Lys), methionine (Met), histidine (His), arginine (Arg), tyrosine (Tyr) and tryptophan (Trp)] were determined by network analyzer and coaxial probe technology. These solutions were heated for (0, 1, 3, 5 min) using microwave irradiation (250 W). Except for Tyr, the dielectric constant of other amino acid solutions gradually decreased with the increasing of frequency at the frequency of 0.3~3 GHz. During microwave heating, the dielectric loss of Arg and Lys solutions tended to decrease with increasing frequency, while other amino acid solutions (except Gln) tended to increase. During the microwave heating process, the dielectric loss of Gln solution displayed an obvious turning point at 0.9 GHz (especially under microwave heated for 3 min and 5 min), which showed a trend of decreasing first and then increasing. The penetration at 915 MHz was higher than 2 450 MHz. When heating for 3 min, the maximum penetration depth of Tyr solution at 915 MHz was (180±0.12) mm, and the maximum penetration depth of Trp solution at 2 450 MHz was (20±1.5) mm. The pH of Arg, Lys solutions decreased due to ionizing during microwave heating. The molecular weight and isoelectric point of amino acids affect the penetration depth of heterocycle amino acid and aliphatic amino acid solutions, and the correlation between the penetration depth of amino acid solution and the molecular weight of amino acid (R²>0.90) was higher than its isoelectric point (R²>0.82). With the increase of heating time, the critical frequencies of heterocyclic amino acids (Tyr, His, Trp, Pro) solutions decreased, whereas the critical frequencies of aliphatic amino acids (Met, Lys, Arg, Gly, Gln, Cys) solutions increased (P<0.05).