We establish an invariant local trace formula for the tangent space of some symmetric spaces over a non-archimedean local field of characteristic zero. These symmetric spaces are studied in Guo-Jacquet trace formulae and our methods are inspired by works of Waldspurger and Arthur. Some other results are given during the proof including a noninvariant local trace formula, Howe's finiteness for weighted orbital integrals and the representability of the Fourier transform of weighted orbital integrals. These local results are prepared for the comparison of regular semi-simple terms, which are weighted orbital integrals, of an infinitesimal variant of Guo-Jacquet trace formulae. Contents 1. Introduction 1 2. Notation and preliminaries 4 3. Symmetric pairs 7 4. Weighted orbital integrals 17 5. The noninvariant trace formula 21 6. Howe's finiteness for weighted orbital integrals 27 7. Representability of the Fourier transform of weighted orbital integrals 33 8. Invariant weighted orbital integrals 41 9. The invariant trace formula 47 10. A vanishing property at infinity 52 References 55 Date: May 4, 2021.Theorem 1.1 (see Theorems 5.3 and 5.12). For all f, f ′ ∈ C ∞ c (s(F )), we have the equalityThis formula results from the Plancherel formula and an analogue of Arthur's truncation process in [5]. We cannot deduce it via the exponential map as in [33, §V] for lack of a local trace formula for symmetric spaces. One needs to return to the proof of [5] instead.In Section 6, we show Howe's finiteness for weighted orbital integrals on s(F ). For r ⊆ s(F ) an open compact subgroup, denote by C ∞ c (s(F )/r) the subspace of C ∞ c (s(F )) consisting of the functions invariant by translation of r.Proposition 1.2 (see Corollaries 6.6 and 6.9). Let r be an open compact subgroup of s(F ), M ∈ L G,ω (M 0 ) and σ ⊆ (m ∩ s rs )(F ). Suppose that there exists a compact subset σ 0 ⊆ (m ∩ s)(F ) such that σ ⊆ Ad((M H )(F ))(σ 0 ). Then there exists a finite subset {X i : i ∈ I} ⊆ σ and a finite subset) such that for all X ∈ σ and all f ∈ C ∞ c (s(F )/r), we have the equalityThe proof originates from Howe's seminal work [18] which is extended to weighted orbital integrals on Lie algebras by Waldspurger. We modify the argument in [33, §IV] to make it apply to our case.In Section 7, we show that the Fourier transform of weighted orbital integrals on s(F ) is represented by locally integrable functions on s(F ).Proposition 1.3 (see Propositions 7.2 and 7.10). Let M ∈ L G,ω (M 0 ) and X ∈ (m ∩ s rs )(F ). Then there exists a locally constant function ĵG M (η, X, •) on s rs (F ) such that for all f ∈ C ∞ c (s(F )), we have