The metatarsophalangeal (MTP) joints play critical roles in the push-off phase of human locomotion, but are usually absent in biped robots. Our previous research found that when the unilateral MTP joints were restricted, non-disabled subjects exerted a compensatory mechanism, that is, the intact limb was relied more than the restricted limb. This paper aims to study the effects of unilateral restrictions of the MTP joints on biped robot walking. Gait performance of a biped robot model was analyzed under two conditions, i.e., walking normally, and walking with the MTP joints of the right foot restricted. The results show that unilateral restrictions of the MTP joints lead to larger demands for driving torque and power on partial joints, more total energy consumption, and lower energy efficiency. These results can help understand the functions of the MTP joints in more depth, and offer some inspirations to the researches of biped robots.