The self-mixing laser Doppler velocitimeter(LDV)system using single mode vertical cavity emitting laser(VCSEL)has better temperature characteristics and wider external cavity length(the optical path length from the laser front mirror to target plate)range compared with the system using multi-mode laser diode. Difference frequency analog phase locked loop(PLL)for small signal processing was used and it obviously improved the velocity measurement accuracy. Triangular wave modulation according to which frequency is divided by the Doppler frequency f_d for direction discrimination was used and it improved its accuracy and dynamic range. The experimental results are as follows: when external length is 30±13 mm,temperature range is 0℃～55℃(no temperature controller for VCSEL),sampling time is 0.1 s,the velocity measurement resolution is better than 0.2% and when velocity measurement range is 30～480 mm/s,the accuracy is better than 0.1% and when the measurement range is 5～480 mm/s,the accuracy is better than 2%. When the supply voltage is 5 V,the forward direction indicating level is higher than 4.9 V and the backward level is lower than 0.1 V.