Abstract： Objective To analyze the amount and tendency of methyl methacrylate(MMA) released from autopolymerized denture base polymer (self-curing resin) during processing using time-of-flight mass spectrometer(TOF-MS). Methods Self-curing resin was mixed in the container using a ratio of 2 g of powder to 1 g of liquid in accordance with the manufacturer's instructions for 40 s as a specimen. The amount of MMA released from the specimen was continuously monitored and simultaneously recorded every minute by TOF-MS since immediately after mixing. A total of five specimens were monitored. Results The amount of MMA increased dramatically at 11 min[(45.2 ±3.5) mg/L] after mixing, and reached the highest level at 13 min[(228.9 ±22.6) mg/L], then become stable at 23 min[(8.8 ±2. 3) mg/L] after mixing. Conclusions The releasing tendency of MMA could be analyzed accurately with continuously monitoring during processing. The amount of MMA released from self-curing resin changed rapidly and the processing was complicated and changeful.