The　fatigue　damage　and　crack　initiation　life　of　40Cr　steel　tempered　at　different　temperatures　were　studied　with　system　analysis　method.　The　influence　of　tempering　temperatures　was　quantitatively　analyzed.　The　relationship　between　the　fatigue　damage　parameter　and　fatigue　crack　initiation　life　of　the　40Cr　steel　were　discussed　and　illustrated.　The　results　show　that　with　increasing　tempering　temperature　the　crack　initiation　life　of　the　40Cr　steel　becomes　longer.　The　crack　initiation　life　of　40Cr　steel　increases　rapidly　with　the　increase　of　tempering　temperatures　below　450°C.　However,　no　significant　increasing　of　crack　initiation　life　of　the　40Cr　steel　is　observed　for　increasing　tempering　temperature　from　450°C　to　580°C.