A thermal desorption low temperature plasma (TD-LTP) ionization source was developed for the direct, rapid and sensitive detection of pesticides by mass spectrometry without complex sample pretreatment. A thermal desorption sampler was added in front of the plasma generator, and the analyte was collected on a polytetrafluoroethylene (PTFE) swab and desorbed into gas molecules, and then gas molecules were transported to the plasma generator by carrier gas to be ionized. The utilization of thermal desorption sampler helped to transform the interaction between gas phase plasma and sample from gas-solid or gas-liquid to gas-gas, which greatly increased the sensitivity and stability especially for non-volatile sample (e.g. pesticides) compared with conventional LTP ionization source. The TD-LTP ionization source was coupled to a homemade rectilinear ion trap mass spectrometry. The operation parameters of the TD-LTP ionization source were optimized and the characteristic ions of 12 different pesticides were successfully obtained and investigated. Then the TD-LTP ionization source was connected with commercial ACQUITY TQD mass spectrometer, and the pesticide residue level in broomcorn was evaluated.