An LED lamp includes: a lamp shell including a lamp head, a lamp neck and a sleeve, the lamp head connects to the lamp neck which connects to the sleeve; a passive heat dissipating element having a heat sink connected to the lamp shell; a power source is disposed in the lamp shell; and a light emitting surface connected to the heat sink of the passive heat dissipating element and comprising LED chips electrically connected to the power source; wherein a lateral outline of the LED lamp detours around an axis of the LED lamp 360 degrees to turn around to form an contour of the LED lamp, any point on the outline meets a formula as follows: y=−ax3+bx2−cx+K; where K is a constant, and range of the constant of K is 360˜450; range of value of a is 0.001˜0.01, range of value of b is 0.05˜0.3, and range of value of c is 5˜20.