Pediococcus acidilactici provides a special taste during dough fermentation, but its improper presence will accelerate the spoilage of rice noodles products. In this study, propidium monoazide (PMA) based methodologies on viable cells quantification of P. acidilactici were developed, evaluated and applied in rice noodles products. Prior to qPCR and RT-qPCR detection, PMA treatment was included to effectively remove the residual DNA from membrane-compromised (dead) cells. Firstly, considering the influence of food component and PMA on qPCR result determination, 4 standard curves corresponding Ct value to P. acidilactici cell number were established in 4 different rice noodle products, respectively. The 4 standard curves were subsequently applied for viable cell quantification of P. acidilactici. Secondly, mimicking the storage conditions of rice noodles products and growth states of P. acidilactici, planktonic and biofilm (early, mediate, mature) cells in 4 types of rice noodles products stored at −20 °C and 4 °C were taken into consideration to evaluate the efficiency of PMA-qPCR for viable cell quantification. Thirdly, stress response gene expression in P. acidilactici was monitored by PMA-RT-qPCR and compared with culturable and viable cell number quantification. The PMA-qPCR method with specific standard curves for 4 types of rice noodle products was applicable for viable cell quantification of P. acidilactici in planktonic and biofilm (early, mediate, and mature) states. The planktonic and biofilm cells of P. acidilactici maintained high and stable in both culturable and viable cell number in different growth states, rice noodles products, and low temperature conditions, but acquired significantly different gene expression levels. The findings provided viable cells quantification methods and an alarm for P. acidilactici contamination risk in instant rice noodles products.