The invention discloses a signal-digit converter of a low-temperature drift rotary transformer. The signal-digit converter is characterized by consisting of a sine and cosine multiplier, an error amplifier, a phase-sensitivity demodulating and phase discriminating device, a voltage-controlled oscillator, a 12-bit reversible counter, a latch, an incremental codec and a serial interface. In the invention, a linear compatible CMOS (Complementary Metal-Oxide-Semiconductor Transistor) process is used; and by adopting a temperature self-compensated bootstrap mirror image current reference source, the invention realizes the output of reference current which is irrelative with mains voltage and near-zero temperature drift near 300K. The sampling precision can be improved by adopting a CMOS switch capacitance technology. All peripheral assemblies are integrated inside an integrated circuit and the most tidy pin definition is formed, so that track conversion from the angle to digital quantity can be realized without extra assemblies. The low-temperature drift can be realized by adopting a zero temperature drift reference source. The wide work frequencies of an input signal and a reference signal can be realized by adopting a dynamic time-delay technology. The high track speed can be realized by adopting a technology of high performance operational amplifier, switch and linear combination and high-speed dynamic parameter design.