A real-time on-line automatic debugging and measuring system for microcomputer compensated crystal oscillator (MCXO) was designed. The system integrates the S&A4220 temperature test chamber, a high precision frequency counter, a personal computer, and a special microcontroller based on C8051F061 with 8 measuring channels. The control program on PC was designed by means of Labview. All main technical parameters of MCXO can be measured automatically with this system. Within the temperature range (-40 ℃ to +85 ℃), the frequency-temperature stability of developed MCXO is ≤±7×10 -8 .