The invention provides an output voltage adjustable CMOS reference voltage source to facilitate the realization of the standard CMOS process, which includes the start circuit, the positive temperature coefficient current generating circuit, the negative temperature coefficient current generating circuit, and the reference voltage generating circuit; the output of the start circuit connecting with the input of the positive temperature coefficient current generating circuit, the first output of the positive temperature coefficient current generating circuit respectively connecting with the first input of the negative temperature coefficient current generating circuit and the third input of the reference voltage generating circuit, the second output of the positive temperature coefficient current generating circuit respectively connecting with the second input of the negative temperature coefficient current generating circuit and the fourth input of the reference voltage generating circuit, the first and second outputs of the negative temperature coefficient current generating circuit respectively corresponding connecting with the first and second inputs of the reference voltage generating circuit, and the reference voltage generating circuit has the reference voltage output to output reference voltage.