An LED lamp includes: a lamp shell including a lamp head, a lamp neck and a sleeve; a passive heat dissipating element having a heat sink connected to the lamp shell; a power source having a first portion and a second portion; 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; a first heat dissipating channel formed in a first chamber of the lamp shell for dissipating heat generated from the power source while the LED lamp is working, and the first chamber is located between bottom of the LED lamp and an upper portion of the lamp neck; and a second heat dissipating channel formed in the heat sink and between the fins and the base of the heat sink for dissipating the heat generated from the LED chips and transferred to the heat sink; 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.