A constant current source with threshold voltage and channel length modulation comprises a set of cascade transistors and a compensation circuit electrically connected to the set of cascade transistors so as to form a feedback circuit, in which the set of cascade transistors including a first MOS transistor and a second MOS transistor, and the compensation circuit comprises a third MOS transistor, a fourth MOS transistor, a sixth MOS transistor and a seventh MOS transistor. The gate terminal of the third MOS transistor is connected to the gate terminal of the second MOS transistor. The fourth MOS transistor is connected to the third MOS transistor in serial, and the gate terminal of the fourth MOS transistor is connected to the gate terminal of the first MOS transistor, and the second terminal of the fourth MOS transistor is connected to a current-supplying circuit. The gate terminals of the sixth and seventh MOS transistors are electrically connected to the current-supplying circuit, and a current is generated by mirroring flows through the third MOS transistor.