The invention discloses an efficient multi-mode DC-DC converter in a wide voltage conversion range. The multi-mode DC-DC converter comprises a Buck-Boost power conversion module, a driving module, a band gap reference module, an IC internal power supply module, a waveform generator module, a working mode selection module, a protection module, a voltage detection module, a current detection module,a soft starting module, a PWM controller module and an LDO controller module. The multi-mode DC-DC converter can realize total integration of a switching tube and a synchronous rectifying tube, and is externally connected with an inductor and an output filter capacitor; the input voltage range is 2.5 to 5.5 volts, the output voltage range of 2.5 to 5.5 volts is adjustable, the maximum output current is 1,000 milliamperes, the maximum working frequency is 1MHz, the precision of the output voltage is less than 5 percent, and a system enters an intermittent working mode during light load to realize the integral system efficiency of more than 80 percent; a control loop adopts double-loop control of voltage and current, realizes the control of a PWM mode and a PFM mode, and can realize LDO control in a specific voltage conversion range; and the over-temperature, over-voltage and over-current protection functions are realized.