A new method for multicarrier optical source generator based on cascaded electro-absorption modulator (EAM) and phase modulator (PM) is proposed. The multicarrier optical source based on single EAM cascaded PM and the multicarrier optical source based on two EAM cascaded PM are studied and analyzed respectively. Multicarrier optical source with frequency interval of 15 GHz, and 19 subcarriers in the range of 0.1 dB flatness using multicarrier optical source generator based on two EAM cascaded PM are achieved. Meanwhile, the influence of the parameters such as modulation index and chirped factor of EAM, modulation signal amplitude of PM, and phase difference of modulators on the multicarrier optical source are also analyzed.