An LED lamp with a flow guide structure guides external air to dissipate heat from the LED lamp includes a lamp base, a heat dissipating body, a heat dissipating plate and an LED module installed in the lamp base, and heat dissipating holes formed on the lamp base. The heat dissipating body includes heat dissipating fins, and a heat dissipating passage defined between any two fins and disposed corresponding to the heat dissipating hole. The LED module is in a thermal contact with the heat dissipating plate. The heat dissipating plate is attached onto the heat dissipating fins and includes openings. A flow guide plate is formed at a lateral edge of each opening and extended from the heat dissipating plate for guiding external air into the heat dissipating passage and out from the heat dissipating hole to expedite a natural convection in the lamp and prevent a thermal aggregation.