Whether forging someone else's signature constitutes a crime needs to be determined in combination with the influence after forgery. If forged IOUs or contracts are forged with forged signatures, causing property losses to others, it constitutes a crime. According to Article 266 of the Criminal Law, whoever defrauds public or private property in a relatively large amount shall be sentenced to fixed-term imprisonment of not more than three years, criminal detention or public surveillance, and shall also or only be fined; If the amount is huge or there are other serious circumstances, he shall be sentenced to fixed-term imprisonment of not less than three years but not more than ten years and shall also be fined; If the amount is especially huge or there are other especially serious circumstances, he shall be sentenced to fixed-term imprisonment of not less than 10 years or life imprisonment, and shall also be fined or confiscated. Where there are other provisions in this Law, such provisions shall prevail.