A laser driver with high-speed and high-current and current modulating method thereof is invented. The laser driver includes a first driving unit and a second driving unit, each driving unit including a pre-drive amplifier circuit and a main drive amplifier circuit. The pre-drive amplifier circuit includes a first differential transistor pair circuit, a differential voltage conversion circuit, a DC common mode level reduction circuit and a first cascode current mirror circuit. The main drive amplifier circuit includes a second differential transistor pair circuit, a bandwidth boost circuit, a matching circuit and a second cascode current mirror circuit. The present invention avoids the enhancement of chip area caused by the use of passive inductors peaking mode to enhance bandwidth, and reduces the cost of chip, design complexity and circuit power consumption.