Based on the analysis of the principle of OCXO,a method to improve the short term stability is proposed.With the design of low phase noise oscillation circuit, high precision temperature control circuit,precision double thermostat and key components selection,a high short term stability OCXO is designed,and the testing method of short term stability is study. Through the test instrument of TSC5115,the short term stability of 10 MHz OCXO reaches to 2×10-13/s,with volume of 65 mm×65 mm×35 mm.