Paecilomyces lilacinus HY-4 is an entomopathogenic filamentous fungus that has exhibited insecticidal activity against Adoretus tenuimaculatus and Tetranychus urticae. Strain HY-4 has attracted a great deal of industrial concerns because this organism can be applicable as a potent bio-pesticide. In this study, we developed an optimal diphasic fermentation technique for HY-4 conidial production. The substrate prescription which was made up of hulls or brans was obtained by screening of agricultural products, and the conidial production could reach a minimum of 2.5×1010 conidia/g after solid fermentation for 12 days in a given condition. It was interesting to note that strain HY-4 was propitious to sporulate more efficiently and productively in liquid fermentation process in the presence of insect pupa. For the industrial application of the HY-4 spores, their pH and thermal stabilities were evaluated on SDA agar plate as well. Additionally, the germination rate of HY-4 spores was still above 90% even when they were stored for 5 months at ambient temperature.