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Nowadays, the plastic injection molding industry is ever-growing, crucial, and its plastic products can be seen everywhere. However, the mold damage problem still frustrates operators because of its high maintenance price and time-consuming maintenance process. This damage is commonly caused by foreign bodies in mold area, and the conventional mold protection method is insufficient for high-performance injection molding machines because of the uncertainty from many setting parameters. To improve detection precision of mold protection driven by a toggle mechanism (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>T</mi> <mi>M</mi> </mrow> </semantics> </math> </inline-formula>), this paper puts forward <inline-formula> <math display="inline"> <semantics> <mrow> <mi>E</mi> <mi>M</mi> <mi>P</mi> </mrow> </semantics> </math> </inline-formula>, i.e., an extended Kalman filter (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>E</mi> <mi>K</mi> <mi>F</mi> </mrow> </semantics> </math> </inline-formula>) based self-adaptive mold protection method, wherein the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>E</mi> <mi>K</mi> <mi>F</mi> </mrow> </semantics> </math> </inline-formula> is used in current curve optimization, and the self-adaptive method (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>S</mi> <mi>A</mi> <mi>M</mi> </mrow> </semantics> </math> </inline-formula>) is proposed to gain an safety range of current curve. The <inline-formula> <math display="inline"> <semantics> <mrow> <mi>E</mi> <mi>M</mi> <mi>P</mi> </mrow> </semantics> </math> </inline-formula> was verified in a 140-ton electric injection molding machine. Compared with a general method, the proposed method decreases the detected distance of mold protection by 22% under different thickness foreign bodies.