The invention discloses a cotton yarn knitting machine. The cotton yarn knitting machine structurally comprises a support frame, a control panel, a thread change break-proof device, a knitting plate,a warning light, a cotton yarn spool, a fixing frame, a motor, a cotton yarn roll and a main body; the control panel is embedded in the front side of the support frame, the control panel is electrically connected with the motor through a wire; the thread change break-proof device is embedded at the upper part of the main body; and the knitting plate is embedded in the main body. The thread changebreak-proof device comprises a thread change device, a starting device, a thread feeding mechanism, a transmission gear, a regulating mechanism, a thread break-proof device and a thin thread removingmechanism; the diameter of a threading hole is manually changed when a thread is changed, the threading efficiency is improved, a thread residue is fixed, the thread conveying stability is improved, the thread is stabilized in the knitting, the dramatic shaking is avoided, the condition that cotton yarn is broken is prevented, thin thread dust produced by friction with the inner part of the deviceis sucked out when a needle and the thread are transferred, and the thread jamming is avoided.