A string compact adjustment apparatus installed on a head of a stringed instrument includes a tuning peg, a pintle, a string holder, a holding ring, a clamp ring and a compact bushing. The pintle runs through the head. The holding ring and clamp ring run through the pintle and fixedly couple on the head. The string holder is fastened to one end of the pintle close to the holding ring, and the tuning peg is fastened to another end thereof. The compact bushing has a contact surface and the clamp ring has a mating latch surface. The compact bushing is pushed by the tuning peg to allow the contact surface to tightly press the latch surface so that the compact bushing is fixedly coupled on the tuning peg and the tuning peg is fixed without turning reversely, thus string tone can be maintained for a long duration.