Telosma mosaic virus (TeMV) is a large virus reported in passion fruit in recent years, and it has a very high infection rate. Guizhou Province is one of the main areas where passion fruit is grown in China. In order to investigate the fact that passion fruit in Guizhou Province carries TeMV, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) method that can effectively detect TeMV was developed. Based on the nucleotide sequence of the TeMV conservative CP gene, six sets of primers were designed, screened, and the real-time turbidimeter was used. The optimized RT-LAMP shows a high degree of specificity for TeMV and the sensitivity is 100 times higher than that of conventional RT-PCR. We used this method to test 60 passion fruit samples collected in Guizhou Province, and the results showed that the detection rate of TeMV in passion fruit in Guizhou Province was 75%. The three TeMV isolates (BXG-GZ1, BXG-GZ2, BXG-GZ3) obtained in the study showed obvious regional specificity based on the phylogenetic analysis. This study provides a visual, simple, fast, highly sensitive and reliable technique for detecting passion fruit TeMV. Meanwhile, this is the first report on the detection of TeMV based on RT-LAMP.