1、信仰不同。
天主教信奉三位（圣父圣子和圣神）一体的天主和耶稣基督，尊玛利亚为圣母。
天主教认为，世界和宇宙中存在一种超自然和超社会的力量，这种力量就是天主。他是独一无二、无所不能、创造有形和无形万物的神。由于他具有三个位格－圣父、圣子、圣神，所以称他为“三位一体”的天主。
基督教认为人类从始祖起就因不遵守上帝的律法而犯了罪，并在罪中悲苦受死，只有信仰三位一体的上帝，借助耶稣基督，才能获救。上帝是基督教信奉的最高唯一真神，是宇宙万物的创造者，并主宰着世界。
2、组织形式不同。
基督教的基本组织被称为教会，基督教认为教会是全体在世和已死基督徒的总体。
天主教会的组织形式严格集中。它重视教阶制，教阶制分为神职教阶和治权教阶。
3、圣经数目不同。
天主教的圣经由《旧约》和《新约》两部分构成，旧约46卷，新约27卷，合计73卷。
基督教圣经包括《旧约圣经》和《新约圣经》，《旧约圣经》即犹太教的《圣经》，是从犹太教承受下来的。旧约39卷，新约27卷，合计66卷。
4、洗礼不同。
天主教的洗礼是具有除罪功效的仪式，认为洗礼可洗去人的原罪。基督教的洗礼是得救之人的见证，与赦罪无关。
天主教与基督教联系：
基督教是一个宗教，所信仰的神是上帝。但是因为种种原因，基督教分为三大流派，分别是天主教、新教、东正教。这三大流派在不同地区的文化背景下，还有各种不同的小的流派。
而基督教的起源是犹太教，双方都信奉上帝，以圣经为经典。但是犹太教不承认耶稣以及圣经新约。基督教徒也因为历史原因对犹太人有意见。
1. Different beliefs.
Catholicism believes in the unity of God and Jesus Christ in three persons (Father, Son and Holy Spirit), and respects Mary as the Virgin. Catholicism believes that there is a supernatural and supersocial power in the world and the universe, and this power is God. He is the unique, omnipotent, creator of all things, visible and invisible. Because he has three persons - the Father, the Son, and the Holy Spirit, he is called the "Trinity" of God.
Christianity believes that human beings have sinned since their ancestors because they did not abide by God's law, and suffered a miserable death in sin. Only by believing in the Trinity God and relying on Jesus Christ can they be saved. God is the highest and only true God believed by Christianity, the creator of all things in the universe, and dominates the world.
2. Different organizational forms.
The basic organization of Christianity is called the church, and Christianity believes that the church is the totality of all living and dead Christians.
The organization of the Catholic Church is strictly centralized. It attaches great importance to the religious hierarchy, which is divided into the priesthood hierarchy and the governing hierarchy.
3. The number of Bibles is different.
The Catholic Bible consists of two parts, the Old Testament and the New Testament. There are 46 volumes in the Old Testament and 27 in the New Testament, making a total of 73 volumes.
The Christian Bible includes the "Old Testament" and the "New Testament". The "Old Testament" is the "Bible" of Judaism, which is inherited from Judaism. There are 39 volumes in the Old Testament and 27 in the New Testament, making a total of 66 volumes.
4. Different baptisms.
Baptism in the Catholic Church is a ritual that has the effect of removing sins. It is believed that baptism can wash away people's original sin. Baptism in Christianity is the testimony of the saved and has nothing to do with the forgiveness of sins.
5、Catholic and Christian Connections:
Christianity is a religion that believes in God. However, due to various reasons, Christianity is divided into three schools: Catholicism, Protestantism, and Orthodox Church. Under the cultural background of these three major genres, there are also various minor genres.
The origin of Christianity is Judaism. Both sides believe in God and take the Bible as the classic. But Judaism does not recognize Jesus and the New Testament of the Bible. Christians also have issues with Jews for historical reasons.