An adjustable prosthetic leg, adapted to be connected between a thigh (A) and an artificial foot (B), comprising: a controller provided with a first pivoting portion and a second pivoting portion , wherein said controller is adapted to be connected to the thigh (A); a hydraulic unit provided with a third pivoting portion , a hydraulic cylinder , a reserve hydraulic cylinder , a brake hydraulic cylinder , an adjust-initiating compartment comprising an elastic element , and a flow system , wherein said hydraulic unit is pivotally connected to said controller so that said hydraulic unit pivots directly about said second pivoting portion , and said hydraulic cylinder , said reserve hydraulic cylinder , and said brake hydraulic cylinder are in communication with each other through said flow system , said flow system having first and second flow paths in communication with both a lower hydraulic compartment of said hydraulic cylinder and said reserve hydraulic cylinder , said first flow path being in communication with said lower hydraulic compartment and said reserve hydraulic cylinder via said brake hydraulic cylinder , and said second flow path bypassing said brake hydraulic cylinder ; a connecting mechanism that is pivotally connected to said controller so that said connecting mechanism pivots directly about said first pivoting portion , and said connecting mechanism extends into said hydraulic cylinder of said hydraulic unit ; and a shell that is pivotally connected to said third pivoting portion and presses against the elastic element in said adjust-initiating compartment , wherein a horizontal angle formed between said second pivoting portion and said third pivoting portion is 40 to 60 degrees, and said shell is further connected to said artificial foot (B). a controller provided with a first pivoting portion and a second pivoting portion , wherein said controller is adapted to be connected to the thigh (A); a hydraulic unit provided with a third pivoting portion , a hydraulic cylinder , a reserve hydraulic cylinder , a brake hydraulic cylinder , an adjust-initiating compartment comprising an elastic element , and a flow system , wherein said hydraulic unit is pivotally connected to said controller so that said hydraulic unit pivots directly about said second pivoting portion , and said hydraulic cylinder , said reserve hydraulic cylinder , and said brake hydraulic cylinder are in communication with each other through said flow system , said flow system having first and second flow paths in communication with both a lower hydraulic compartment of said hydraulic cylinder and said reserve hydraulic cylinder , said first flow path being in communication with said lower hydraulic compartment and said reserve hydraulic cylinder via said brake hydraulic cylinder , and said second flow path bypassing said brake hydraulic cylinder ; a connecting mechanism that is pivotally connected to said controller so that said connecting mechanism pivots directly about said first pivoting portion , and said connecting mechanism extends into said hydraulic cylinder of said hydraulic unit ; and a shell that is pivotally connected to said third pivoting portion and presses against the elastic element in said adjust-initiating compartment , wherein a horizontal angle formed between said second pivoting portion and said third pivoting portion is 40 to 60 degrees, and said shell is further connected to said artificial foot (B). <EOS>