To investigate the influence of the variable stator vane partial gap of the axial compressor front stage on the performance of the compressor and the flow field, numerical simulation was carried out on the front 1.5 stage axial compressor consisted of a variable stator vane, and the detailed analysis was conducted on the flow characteristics of the partial gap leakage flow. The numerical simulation results show that the performance curve shifts downwards and left due to the effect of the partial gap compared with the prototype cavity case. The efficiency decreased 0.12% at the design point (DP) working condition and 1.83% at the near stall (NS) working condition respectively and the stall margin (SM) increased 6.4%. The outlet flow angle of S3 at the hub region increased due to the partial gap leakage flow. The partial gap leakage flow can charge the low momentum fluid at the hub corner region, therefore, the total pressure loss coefficient decreased at DP working condition. The separation vortices at the suction side can be weakened by the partial gap leakage flow and the stall margin will be improved. The blade can not provide sufficient working capacity but the range is limited below 5% span. The flow field at the hub region changed due to the partial gap, an attachment line formed at the hub region at the suction side and involved into closed separation.