The high speed coaxial laser diode assembly with data rate up to 10 Gb/s and transmitting distance up to 10 km is studied. Based on the in-depth analysis of the key characteristic inside the assembly covering from optical structure to high frequency electrical performance,and after a series of optimized design,the transmitter optical sub-assembly (TOSA) has been developed successfully,which can be directly adopted by 10 Gb/s small factor XFP transceiver. The final test shows that better than 7 dB extinction ratio and margin of more than 15% at 10.709 Gb/s are obtained,which keeps well compatible with the one of those advanced level products over the world.